GitLab

Previosly plugin code was using PluginMessageLoopProxy that implements
MessageLoopProxy interface. We no longer need MessageLoopProxy.
Replacing PluginMessageLoopProxy with PluginThreadTaskRunner that
implements SingleThreadTaskRunner interface


Review URL: https://chromiumcodereview.appspot.com/10830016

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@148801 0039d316-1c4b-4281-b951-d872f2087c98