Replace some callers of staleInCompositingMode.

There's no change in behavior here other than adding asserts.
I tested this by running webkit_unit_tests and the layout tests.

Review URL: https://codereview.chromium.org/253533002

git-svn-id: svn://svn.chromium.org/blink/trunk@172655 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Add the backchannel for Blobs to be received into Blink from the database backend.

BUG=108012

Review URL: https://codereview.chromium.org/235933013

git-svn-id: svn://svn.chromium.org/blink/trunk@172656 bbb929c8-8fbe-4397-9dbb-9b2b20218538