chrome/browser/metrics/field_trial_synchronizer.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 "chrome/browser/metrics/field_trial_synchronizer.h"
   6
   7 #include "base/bind.h"
   8 #include "base/logging.h"
   9 #include "base/threading/thread.h"
  10 #include "chrome/common/chrome_constants.h"
  11 #include "chrome/common/metrics/variations/variations_util.h"
  12 #include "chrome/common/render_messages.h"
  13 #include "content/public/browser/browser_thread.h"
  14 #include "content/public/browser/render_process_host.h"
  15
  16 using content::BrowserThread;
  17
  18 namespace {
  19
  20 // This singleton instance should be constructed during the single threaded
  21 // portion of main(). It initializes globals to provide support for all future
  22 // calls. This object is created on the UI thread, and it is destroyed after
  23 // all the other threads have gone away.
  24 FieldTrialSynchronizer* g_field_trial_synchronizer = NULL;
  25
  26 }  // namespace
  27
  28 FieldTrialSynchronizer::FieldTrialSynchronizer() {
  29   DCHECK(g_field_trial_synchronizer == NULL);
  30   g_field_trial_synchronizer = this;
  31   base::FieldTrialList::AddObserver(this);
  32
  33   chrome_variations::SetChildProcessLoggingVariationList();
  34 }
  35
  36 void FieldTrialSynchronizer::NotifyAllRenderers(
  37     const std::string& field_trial_name,
  38     const std::string& group_name) {
  39   // To iterate over RenderProcessHosts, or to send messages to the hosts, we
  40   // need to be on the UI thread.
  41   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  42
  43   for (content::RenderProcessHost::iterator it(
  44           content::RenderProcessHost::AllHostsIterator());
  45        !it.IsAtEnd(); it.Advance()) {
  46     it.GetCurrentValue()->Send(
  47         new ChromeViewMsg_SetFieldTrialGroup(field_trial_name, group_name));
  48   }
  49 }
  50
  51 void FieldTrialSynchronizer::OnFieldTrialGroupFinalized(
  52     const std::string& field_trial_name,
  53     const std::string& group_name) {
  54   BrowserThread::PostTask(
  55       BrowserThread::UI, FROM_HERE,
  56       base::Bind(&FieldTrialSynchronizer::NotifyAllRenderers,
  57                  this,
  58                  field_trial_name,
  59                  group_name));
  60   chrome_variations::SetChildProcessLoggingVariationList();
  61 }
  62
  63 FieldTrialSynchronizer::~FieldTrialSynchronizer() {
  64   base::FieldTrialList::RemoveObserver(this);
  65   g_field_trial_synchronizer = NULL;
  66 }