Fix for accelerated canvas layer content invalidation

The fixes a display invalidation bug that exists only in M-38
This change must be reverted from trunk after it is merged to
the release branch.  This change disables a renctly added
optimization that that performs partial display invalidations
on 2d canvas layers.

BUG=417201

Review URL: https://codereview.chromium.org/601183004

git-svn-id: svn://svn.chromium.org/blink/trunk@182690 bbb929c8-8fbe-4397-9dbb-9b2b20218538