Revert: Flapper field trial to use workerpool for sync file operations.

Original: https://chromiumcodereview.appspot.com/11016016

The field trial indicated a 20% improvement using blocking workerpool.
That seems worth merging to M-23.  Revert the change so that a clean
change can be landed and drover'ed over.

BUG=153383
[email protected]

Review URL: https://codereview.chromium.org/11087068

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@161253 0039d316-1c4b-4281-b951-d872f2087c98
3 files changed