cc: Move internal::Task::did_schedule_ to internal::WorkerPoolTask.

This moves the task scheduling notion out of the TaskGraphRunner and
into the RasterWorkerPool. This is a more appropriate place to handle
this and required as tasks need to complete multiple times when used
with PixelRasterWorkerPool.

BUG=339201

Review URL: https://codereview.chromium.org/140333006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249236 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249236