content_shell: Use a ThreadRestrictions::ScopedAllowWait for layout tests on Android.

content_shell: Use a ThreadRestrictions::ScopedAllowWait for layout tests on Android.

Because of the nested message pump implementation used by Android for
running layout tests, which uses a base::WaitableEvent to wait for new
messages, we need to allow waiting on the UI thread.

The ScopedAllowWaitForAndroidLayoutTest class has been implemented as
a member of the WebKitTestController, to ensure that the exception's
lifetime is tied to the layout test controller itself.

BUG=232044
R=jam@chromium.org, jochen@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=207523

[jochen (gone - plz use gerrit), 2013-06-18 18:20:26]

lgtm

[jam, 2013-06-18 23:21:19]

lgtm

[commit-bot: I haz the power, 2013-06-18 23:42:07]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/peter@chromium.org/17395002/4001

[commit-bot: I haz the power, 2013-06-19 00:23:07]

Sorry for I got bad news for ya.
Compile failed with a clobber build on android_dbg.
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=android_db...
Your code is likely broken or HEAD is junk. Please ensure your
code is not broken then alert the build sheriffs.
Look at the try server FAQ for more details.

[commit-bot: I haz the power, 2013-06-19 10:46:52]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/peter@chromium.org/17395002/3003

[Peter Beverloo, 2013-06-20 20:02:38]

Committed patchset #4 manually as r207523 (presubmit successful).