Revert of Better handle reentrancy into DocumentLoader::dataReceived(). (patchset...

Revert of Better handle reentrancy into DocumentLoader::dataReceived(). (patchset #10 id:180001 of https://codereview.chromium.org/1263363005/ )

Reason for revert:
ASan bots are reporting a handful of UAFs,

 http://build.chromium.org/p/chromium.webkit/builders/WebKit%20Linux%20ASAN/builds/19837

Original issue's description:
> Better handle reentrancy into DocumentLoader::dataReceived().
>
> dataReceived() can be called reentrantly if it triggers a nested message
> loop when detaching a Document or parsing script for the new Document.
> Since dataReceived() isn't safe for reentrancy, any nested invocations
> queue the received data to be processed by the top-level invocation of
> dataReceived().
>
> BUG=515876
>
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=200436

TBR=japhet@chromium.org,kouhei@chromium.org,morrita@chromium.org,dcheng@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=515876

Review URL: https://codereview.chromium.org/1295553002

git-svn-id: svn://svn.chromium.org/blink/trunk@200487 bbb929c8-8fbe-4397-9dbb-9b2b20218538