content/browser/storage_partition_impl_map.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "content/browser/storage_partition_impl_map.h"
   6
   7 #include "base/bind.h"
   8 #include "base/callback.h"
   9 #include "base/file_util.h"
  10 #include "base/files/file_enumerator.h"
  11 #include "base/files/file_path.h"
  12 #include "base/stl_util.h"
  13 #include "base/strings/string_number_conversions.h"
  14 #include "base/strings/string_util.h"
  15 #include "base/strings/stringprintf.h"
  16 #include "base/threading/sequenced_worker_pool.h"
  17 #include "content/browser/appcache/chrome_appcache_service.h"
  18 #include "content/browser/fileapi/browser_file_system_helper.h"
  19 #include "content/browser/fileapi/chrome_blob_storage_context.h"
  20 #include "content/browser/loader/resource_request_info_impl.h"
  21 #include "content/browser/resource_context_impl.h"
  22 #include "content/browser/service_worker/service_worker_request_handler.h"
  23 #include "content/browser/storage_partition_impl.h"
  24 #include "content/browser/streams/stream.h"
  25 #include "content/browser/streams/stream_context.h"
  26 #include "content/browser/streams/stream_registry.h"
  27 #include "content/browser/streams/stream_url_request_job.h"
  28 #include "content/browser/webui/url_data_manager_backend.h"
  29 #include "content/public/browser/browser_context.h"
  30 #include "content/public/browser/browser_thread.h"
  31 #include "content/public/browser/content_browser_client.h"
  32 #include "content/public/browser/storage_partition.h"
  33 #include "content/public/common/content_constants.h"
  34 #include "content/public/common/url_constants.h"
  35 #include "crypto/sha2.h"
  36 #include "net/url_request/url_request_context.h"
  37 #include "net/url_request/url_request_context_getter.h"
  38 #include "webkit/browser/blob/blob_storage_context.h"
  39 #include "webkit/browser/blob/blob_url_request_job_factory.h"
  40 #include "webkit/browser/fileapi/file_system_url_request_job_factory.h"
  41 #include "webkit/common/blob/blob_data.h"
  42
  43 using appcache::AppCacheService;
  44 using fileapi::FileSystemContext;
  45 using webkit_blob::BlobStorageContext;
  46
  47 namespace content {
  48
  49 namespace {
  50
  51 // A derivative that knows about Streams too.
  52 class BlobProtocolHandler : public net::URLRequestJobFactory::ProtocolHandler {
  53  public:
  54   BlobProtocolHandler(ChromeBlobStorageContext* blob_storage_context,
  55                       StreamContext* stream_context,
  56                       fileapi::FileSystemContext* file_system_context)
  57       : blob_storage_context_(blob_storage_context),
  58         stream_context_(stream_context),
  59         file_system_context_(file_system_context) {
  60   }
  61
  62   virtual ~BlobProtocolHandler() {
  63   }
  64
  65   virtual net::URLRequestJob* MaybeCreateJob(
  66       net::URLRequest* request,
  67       net::NetworkDelegate* network_delegate) const OVERRIDE {
  68     scoped_refptr<Stream> stream =
  69         stream_context_->registry()->GetStream(request->url());
  70     if (stream.get())
  71       return new StreamURLRequestJob(request, network_delegate, stream);
  72
  73     if (!blob_protocol_handler_) {
  74       // Construction is deferred because 'this' is constructed on
  75       // the main thread but we want blob_protocol_handler_ constructed
  76       // on the IO thread.
  77       blob_protocol_handler_.reset(
  78           new webkit_blob::BlobProtocolHandler(
  79               blob_storage_context_->context(),
  80               file_system_context_,
  81               BrowserThread::GetMessageLoopProxyForThread(
  82                   BrowserThread::FILE).get()));
  83     }
  84     return blob_protocol_handler_->MaybeCreateJob(request, network_delegate);
  85   }
  86
  87  private:
  88   const scoped_refptr<ChromeBlobStorageContext> blob_storage_context_;
  89   const scoped_refptr<StreamContext> stream_context_;
  90   const scoped_refptr<fileapi::FileSystemContext> file_system_context_;
  91   mutable scoped_ptr<webkit_blob::BlobProtocolHandler> blob_protocol_handler_;
  92   DISALLOW_COPY_AND_ASSIGN(BlobProtocolHandler);
  93 };
  94
  95 // These constants are used to create the directory structure under the profile
  96 // where renderers with a non-default storage partition keep their persistent
  97 // state. This will contain a set of directories that partially mirror the
  98 // directory structure of BrowserContext::GetPath().
  99 //
 100 // The kStoragePartitionDirname contains an extensions directory which is
 101 // further partitioned by extension id, followed by another level of directories
 102 // for the "default" extension storage partition and one directory for each
 103 // persistent partition used by a webview tag. Example:
 104 //
 105 //   Storage/ext/ABCDEF/def
 106 //   Storage/ext/ABCDEF/hash(partition name)
 107 //
 108 // The code in GetStoragePartitionPath() constructs these path names.
 109 //
 110 // TODO(nasko): Move extension related path code out of content.
 111 const base::FilePath::CharType kStoragePartitionDirname[] =
 112     FILE_PATH_LITERAL("Storage");
 113 const base::FilePath::CharType kExtensionsDirname[] =
 114     FILE_PATH_LITERAL("ext");
 115 const base::FilePath::CharType kDefaultPartitionDirname[] =
 116     FILE_PATH_LITERAL("def");
 117 const base::FilePath::CharType kTrashDirname[] =
 118     FILE_PATH_LITERAL("trash");
 119
 120 // Because partition names are user specified, they can be arbitrarily long
 121 // which makes them unsuitable for paths names. We use a truncation of a
 122 // SHA256 hash to perform a deterministic shortening of the string. The
 123 // kPartitionNameHashBytes constant controls the length of the truncation.
 124 // We use 6 bytes, which gives us 99.999% reliability against collisions over
 125 // 1 million partition domains.
 126 //
 127 // Analysis:
 128 // We assume that all partition names within one partition domain are
 129 // controlled by the the same entity. Thus there is no chance for adverserial
 130 // attack and all we care about is accidental collision. To get 5 9s over
 131 // 1 million domains, we need the probability of a collision in any one domain
 132 // to be
 133 //
 134 //    p < nroot(1000000, .99999) ~= 10^-11
 135 //
 136 // We use the following birthday attack approximation to calculate the max
 137 // number of unique names for this probability:
 138 //
 139 //    n(p,H) = sqrt(2*H * ln(1/(1-p)))
 140 //
 141 // For a 6-byte hash, H = 2^(6*8).  n(10^-11, H) ~= 75
 142 //
 143 // An average partition domain is likely to have less than 10 unique
 144 // partition names which is far lower than 75.
 145 //
 146 // Note, that for 4 9s of reliability, the limit is 237 partition names per
 147 // partition domain.
 148 const int kPartitionNameHashBytes = 6;
 149
 150 // Needed for selecting all files in ObliterateOneDirectory() below.
 151 #if defined(OS_POSIX)
 152 const int kAllFileTypes = base::FileEnumerator::FILES |
 153                           base::FileEnumerator::DIRECTORIES |
 154                           base::FileEnumerator::SHOW_SYM_LINKS;
 155 #else
 156 const int kAllFileTypes = base::FileEnumerator::FILES |
 157                           base::FileEnumerator::DIRECTORIES;
 158 #endif
 159
 160 base::FilePath GetStoragePartitionDomainPath(
 161     const std::string& partition_domain) {
 162   CHECK(IsStringUTF8(partition_domain));
 163
 164   return base::FilePath(kStoragePartitionDirname).Append(kExtensionsDirname)
 165       .Append(base::FilePath::FromUTF8Unsafe(partition_domain));
 166 }
 167
 168 // Helper function for doing a depth-first deletion of the data on disk.
 169 // Examines paths directly in |current_dir| (no recursion) and tries to
 170 // delete from disk anything that is in, or isn't a parent of something in
 171 // |paths_to_keep|. Paths that need further expansion are added to
 172 // |paths_to_consider|.
 173 void ObliterateOneDirectory(const base::FilePath& current_dir,
 174                             const std::vector<base::FilePath>& paths_to_keep,
 175                             std::vector<base::FilePath>* paths_to_consider) {
 176   CHECK(current_dir.IsAbsolute());
 177
 178   base::FileEnumerator enumerator(current_dir, false, kAllFileTypes);
 179   for (base::FilePath to_delete = enumerator.Next(); !to_delete.empty();
 180        to_delete = enumerator.Next()) {
 181     // Enum tracking which of the 3 possible actions to take for |to_delete|.
 182     enum { kSkip, kEnqueue, kDelete } action = kDelete;
 183
 184     for (std::vector<base::FilePath>::const_iterator to_keep =
 185              paths_to_keep.begin();
 186          to_keep != paths_to_keep.end();
 187          ++to_keep) {
 188       if (to_delete == *to_keep) {
 189         action = kSkip;
 190         break;
 191       } else if (to_delete.IsParent(*to_keep)) {
 192         // |to_delete| contains a path to keep. Add to stack for further
 193         // processing.
 194         action = kEnqueue;
 195         break;
 196       }
 197     }
 198
 199     switch (action) {
 200       case kDelete:
 201         base::DeleteFile(to_delete, true);
 202         break;
 203
 204       case kEnqueue:
 205         paths_to_consider->push_back(to_delete);
 206         break;
 207
 208       case kSkip:
 209         break;
 210     }
 211   }
 212 }
 213
 214 // Synchronously attempts to delete |unnormalized_root|, preserving only
 215 // entries in |paths_to_keep|. If there are no entries in |paths_to_keep| on
 216 // disk, then it completely removes |unnormalized_root|. All paths must be
 217 // absolute paths.
 218 void BlockingObliteratePath(
 219     const base::FilePath& unnormalized_browser_context_root,
 220     const base::FilePath& unnormalized_root,
 221     const std::vector<base::FilePath>& paths_to_keep,
 222     const scoped_refptr<base::TaskRunner>& closure_runner,
 223     const base::Closure& on_gc_required) {
 224   // Early exit required because MakeAbsoluteFilePath() will fail on POSIX
 225   // if |unnormalized_root| does not exist. This is safe because there is
 226   // nothing to do in this situation anwyays.
 227   if (!base::PathExists(unnormalized_root)) {
 228     return;
 229   }
 230
 231   // Never try to obliterate things outside of the browser context root or the
 232   // browser context root itself. Die hard.
 233   base::FilePath root = base::MakeAbsoluteFilePath(unnormalized_root);
 234   base::FilePath browser_context_root =
 235       base::MakeAbsoluteFilePath(unnormalized_browser_context_root);
 236   CHECK(!root.empty());
 237   CHECK(!browser_context_root.empty());
 238   CHECK(browser_context_root.IsParent(root) && browser_context_root != root);
 239
 240   // Reduce |paths_to_keep| set to those under the root and actually on disk.
 241   std::vector<base::FilePath> valid_paths_to_keep;
 242   for (std::vector<base::FilePath>::const_iterator it = paths_to_keep.begin();
 243        it != paths_to_keep.end();
 244        ++it) {
 245     if (root.IsParent(*it) && base::PathExists(*it))
 246       valid_paths_to_keep.push_back(*it);
 247   }
 248
 249   // If none of the |paths_to_keep| are valid anymore then we just whack the
 250   // root and be done with it.  Otherwise, signal garbage collection and do
 251   // a best-effort delete of the on-disk structures.
 252   if (valid_paths_to_keep.empty()) {
 253     base::DeleteFile(root, true);
 254     return;
 255   }
 256   closure_runner->PostTask(FROM_HERE, on_gc_required);
 257
 258   // Otherwise, start at the root and delete everything that is not in
 259   // |valid_paths_to_keep|.
 260   std::vector<base::FilePath> paths_to_consider;
 261   paths_to_consider.push_back(root);
 262   while(!paths_to_consider.empty()) {
 263     base::FilePath path = paths_to_consider.back();
 264     paths_to_consider.pop_back();
 265     ObliterateOneDirectory(path, valid_paths_to_keep, &paths_to_consider);
 266   }
 267 }
 268
 269 // Deletes all entries inside the |storage_root| that are not in the
 270 // |active_paths|.  Deletion is done in 2 steps:
 271 //
 272 //   (1) Moving all garbage collected paths into a trash directory.
 273 //   (2) Asynchronously deleting the trash directory.
 274 //
 275 // The deletion is asynchronous because after (1) completes, calling code can
 276 // safely continue to use the paths that had just been garbage collected
 277 // without fear of race conditions.
 278 //
 279 // This code also ignores failed moves rather than attempting a smarter retry.
 280 // Moves shouldn't fail here unless there is some out-of-band error (eg.,
 281 // FS corruption). Retry logic is dangerous in the general case because
 282 // there is not necessarily a guaranteed case where the logic may succeed.
 283 //
 284 // This function is still named BlockingGarbageCollect() because it does
 285 // execute a few filesystem operations synchronously.
 286 void BlockingGarbageCollect(
 287     const base::FilePath& storage_root,
 288     const scoped_refptr<base::TaskRunner>& file_access_runner,
 289     scoped_ptr<base::hash_set<base::FilePath> > active_paths) {
 290   CHECK(storage_root.IsAbsolute());
 291
 292   base::FileEnumerator enumerator(storage_root, false, kAllFileTypes);
 293   base::FilePath trash_directory;
 294   if (!base::CreateTemporaryDirInDir(storage_root, kTrashDirname,
 295                                      &trash_directory)) {
 296     // Unable to continue without creating the trash directory so give up.
 297     return;
 298   }
 299   for (base::FilePath path = enumerator.Next(); !path.empty();
 300        path = enumerator.Next()) {
 301     if (active_paths->find(path) == active_paths->end() &&
 302         path != trash_directory) {
 303       // Since |trash_directory| is unique for each run of this function there
 304       // can be no colllisions on the move.
 305       base::Move(path, trash_directory.Append(path.BaseName()));
 306     }
 307   }
 308
 309   file_access_runner->PostTask(
 310       FROM_HERE,
 311       base::Bind(base::IgnoreResult(&base::DeleteFile), trash_directory, true));
 312 }
 313
 314 }  // namespace
 315
 316 // static
 317 base::FilePath StoragePartitionImplMap::GetStoragePartitionPath(
 318     const std::string& partition_domain,
 319     const std::string& partition_name) {
 320   if (partition_domain.empty())
 321     return base::FilePath();
 322
 323   base::FilePath path = GetStoragePartitionDomainPath(partition_domain);
 324
 325   // TODO(ajwong): Mangle in-memory into this somehow, either by putting
 326   // it into the partition_name, or by manually adding another path component
 327   // here.  Otherwise, it's possible to have an in-memory StoragePartition and
 328   // a persistent one that return the same FilePath for GetPath().
 329   if (!partition_name.empty()) {
 330     // For analysis of why we can ignore collisions, see the comment above
 331     // kPartitionNameHashBytes.
 332     char buffer[kPartitionNameHashBytes];
 333     crypto::SHA256HashString(partition_name, &buffer[0],
 334                              sizeof(buffer));
 335     return path.AppendASCII(base::HexEncode(buffer, sizeof(buffer)));
 336   }
 337
 338   return path.Append(kDefaultPartitionDirname);
 339 }
 340
 341 StoragePartitionImplMap::StoragePartitionImplMap(
 342     BrowserContext* browser_context)
 343     : browser_context_(browser_context),
 344       resource_context_initialized_(false) {
 345   // Doing here instead of initializer list cause it's just too ugly to read.
 346   base::SequencedWorkerPool* blocking_pool = BrowserThread::GetBlockingPool();
 347   file_access_runner_ =
 348       blocking_pool->GetSequencedTaskRunner(blocking_pool->GetSequenceToken());
 349 }
 350
 351 StoragePartitionImplMap::~StoragePartitionImplMap() {
 352   STLDeleteContainerPairSecondPointers(partitions_.begin(),
 353                                        partitions_.end());
 354 }
 355
 356 StoragePartitionImpl* StoragePartitionImplMap::Get(
 357     const std::string& partition_domain,
 358     const std::string& partition_name,
 359     bool in_memory) {
 360   // Find the previously created partition if it's available.
 361   StoragePartitionConfig partition_config(
 362       partition_domain, partition_name, in_memory);
 363
 364   PartitionMap::const_iterator it = partitions_.find(partition_config);
 365   if (it != partitions_.end())
 366     return it->second;
 367
 368   base::FilePath partition_path =
 369       browser_context_->GetPath().Append(
 370           GetStoragePartitionPath(partition_domain, partition_name));
 371   StoragePartitionImpl* partition =
 372       StoragePartitionImpl::Create(browser_context_, in_memory,
 373                                    partition_path);
 374   partitions_[partition_config] = partition;
 375
 376   ChromeBlobStorageContext* blob_storage_context =
 377       ChromeBlobStorageContext::GetFor(browser_context_);
 378   StreamContext* stream_context = StreamContext::GetFor(browser_context_);
 379   ProtocolHandlerMap protocol_handlers;
 380   protocol_handlers[kBlobScheme] =
 381       linked_ptr<net::URLRequestJobFactory::ProtocolHandler>(
 382           new BlobProtocolHandler(blob_storage_context,
 383                                   stream_context,
 384                                   partition->GetFileSystemContext()));
 385   protocol_handlers[kFileSystemScheme] =
 386       linked_ptr<net::URLRequestJobFactory::ProtocolHandler>(
 387           CreateFileSystemProtocolHandler(partition_domain,
 388                                           partition->GetFileSystemContext()));
 389   protocol_handlers[kChromeUIScheme] =
 390       linked_ptr<net::URLRequestJobFactory::ProtocolHandler>(
 391           URLDataManagerBackend::CreateProtocolHandler(
 392               browser_context_->GetResourceContext(),
 393               browser_context_->IsOffTheRecord(),
 394               partition->GetAppCacheService(),
 395               blob_storage_context));
 396   std::vector<std::string> additional_webui_schemes;
 397   GetContentClient()->browser()->GetAdditionalWebUISchemes(
 398       &additional_webui_schemes);
 399   for (std::vector<std::string>::const_iterator it =
 400            additional_webui_schemes.begin();
 401        it != additional_webui_schemes.end();
 402        ++it) {
 403     protocol_handlers[*it] =
 404         linked_ptr<net::URLRequestJobFactory::ProtocolHandler>(
 405             URLDataManagerBackend::CreateProtocolHandler(
 406                 browser_context_->GetResourceContext(),
 407                 browser_context_->IsOffTheRecord(),
 408                 partition->GetAppCacheService(),
 409                 blob_storage_context));
 410   }
 411   protocol_handlers[kChromeDevToolsScheme] =
 412       linked_ptr<net::URLRequestJobFactory::ProtocolHandler>(
 413           CreateDevToolsProtocolHandler(browser_context_->GetResourceContext(),
 414                                         browser_context_->IsOffTheRecord()));
 415
 416   ProtocolHandlerScopedVector protocol_interceptors;
 417   protocol_interceptors.push_back(
 418       ServiceWorkerRequestHandler::CreateInterceptor().release());
 419
 420   // These calls must happen after StoragePartitionImpl::Create().
 421   if (partition_domain.empty()) {
 422     partition->SetURLRequestContext(
 423         GetContentClient()->browser()->CreateRequestContext(
 424             browser_context_,
 425             &protocol_handlers,
 426             protocol_interceptors.Pass()));
 427   } else {
 428     partition->SetURLRequestContext(
 429         GetContentClient()->browser()->CreateRequestContextForStoragePartition(
 430             browser_context_,
 431             partition->GetPath(),
 432             in_memory,
 433             &protocol_handlers,
 434             protocol_interceptors.Pass()));
 435   }
 436   partition->SetMediaURLRequestContext(
 437       partition_domain.empty() ?
 438       browser_context_->GetMediaRequestContext() :
 439       browser_context_->GetMediaRequestContextForStoragePartition(
 440           partition->GetPath(), in_memory));
 441
 442   PostCreateInitialization(partition, in_memory);
 443
 444   return partition;
 445 }
 446
 447 void StoragePartitionImplMap::AsyncObliterate(
 448     const GURL& site,
 449     const base::Closure& on_gc_required) {
 450   // This method should avoid creating any StoragePartition (which would
 451   // create more open file handles) so that it can delete as much of the
 452   // data off disk as possible.
 453   std::string partition_domain;
 454   std::string partition_name;
 455   bool in_memory = false;
 456   GetContentClient()->browser()->GetStoragePartitionConfigForSite(
 457       browser_context_, site, false, &partition_domain,
 458       &partition_name, &in_memory);
 459
 460   // Find the active partitions for the domain. Because these partitions are
 461   // active, it is not possible to just delete the directories that contain
 462   // the backing data structures without causing the browser to crash. Instead,
 463   // of deleteing the directory, we tell each storage context later to
 464   // remove any data they have saved. This will leave the directory structure
 465   // intact but it will only contain empty databases.
 466   std::vector<StoragePartitionImpl*> active_partitions;
 467   std::vector<base::FilePath> paths_to_keep;
 468   for (PartitionMap::const_iterator it = partitions_.begin();
 469        it != partitions_.end();
 470        ++it) {
 471     const StoragePartitionConfig& config = it->first;
 472     if (config.partition_domain == partition_domain) {
 473       it->second->ClearData(
 474           // All except shader cache.
 475           StoragePartition::REMOVE_DATA_MASK_ALL &
 476             (~StoragePartition::REMOVE_DATA_MASK_SHADER_CACHE),
 477           StoragePartition::QUOTA_MANAGED_STORAGE_MASK_ALL,
 478           GURL(),
 479           StoragePartition::OriginMatcherFunction(),
 480           base::Time(), base::Time::Max(),
 481           base::Bind(&base::DoNothing));
 482       if (!config.in_memory) {
 483         paths_to_keep.push_back(it->second->GetPath());
 484       }
 485     }
 486   }
 487
 488   // Start a best-effort delete of the on-disk storage excluding paths that are
 489   // known to still be in use. This is to delete any previously created
 490   // StoragePartition state that just happens to not have been used during this
 491   // run of the browser.
 492   base::FilePath domain_root = browser_context_->GetPath().Append(
 493       GetStoragePartitionDomainPath(partition_domain));
 494
 495   BrowserThread::PostBlockingPoolTask(
 496       FROM_HERE,
 497       base::Bind(&BlockingObliteratePath, browser_context_->GetPath(),
 498                  domain_root, paths_to_keep,
 499                  base::MessageLoopProxy::current(), on_gc_required));
 500 }
 501
 502 void StoragePartitionImplMap::GarbageCollect(
 503     scoped_ptr<base::hash_set<base::FilePath> > active_paths,
 504     const base::Closure& done) {
 505   // Include all paths for current StoragePartitions in the active_paths since
 506   // they cannot be deleted safely.
 507   for (PartitionMap::const_iterator it = partitions_.begin();
 508        it != partitions_.end();
 509        ++it) {
 510     const StoragePartitionConfig& config = it->first;
 511     if (!config.in_memory)
 512       active_paths->insert(it->second->GetPath());
 513   }
 514
 515   // Find the directory holding the StoragePartitions and delete everything in
 516   // there that isn't considered active.
 517   base::FilePath storage_root = browser_context_->GetPath().Append(
 518       GetStoragePartitionDomainPath(std::string()));
 519   file_access_runner_->PostTaskAndReply(
 520       FROM_HERE,
 521       base::Bind(&BlockingGarbageCollect, storage_root,
 522                  file_access_runner_,
 523                  base::Passed(&active_paths)),
 524       done);
 525 }
 526
 527 void StoragePartitionImplMap::ForEach(
 528     const BrowserContext::StoragePartitionCallback& callback) {
 529   for (PartitionMap::const_iterator it = partitions_.begin();
 530        it != partitions_.end();
 531        ++it) {
 532     callback.Run(it->second);
 533   }
 534 }
 535
 536 void StoragePartitionImplMap::PostCreateInitialization(
 537     StoragePartitionImpl* partition,
 538     bool in_memory) {
 539   // TODO(ajwong): ResourceContexts no longer have any storage related state.
 540   // We should move this into a place where it is called once per
 541   // BrowserContext creation rather than piggybacking off the default context
 542   // creation.
 543   // Note: moving this into Get() before partitions_[] is set causes reentrency.
 544   if (!resource_context_initialized_) {
 545     resource_context_initialized_ = true;
 546     InitializeResourceContext(browser_context_);
 547   }
 548
 549   // Check first to avoid memory leak in unittests.
 550   if (BrowserThread::IsMessageLoopValid(BrowserThread::IO)) {
 551     BrowserThread::PostTask(
 552         BrowserThread::IO, FROM_HERE,
 553         base::Bind(&ChromeAppCacheService::InitializeOnIOThread,
 554                    partition->GetAppCacheService(),
 555                    in_memory ? base::FilePath() :
 556                        partition->GetPath().Append(kAppCacheDirname),
 557                    browser_context_->GetResourceContext(),
 558                    make_scoped_refptr(partition->GetURLRequestContext()),
 559                    make_scoped_refptr(
 560                        browser_context_->GetSpecialStoragePolicy())));
 561
 562     // We do not call InitializeURLRequestContext() for media contexts because,
 563     // other than the HTTP cache, the media contexts share the same backing
 564     // objects as their associated "normal" request context.  Thus, the previous
 565     // call serves to initialize the media request context for this storage
 566     // partition as well.
 567   }
 568 }
 569
 570 }  // namespace content