Add compositorDrivenAcceleratedScrollingEnabled setting in Internals.

This is to control an upcoming feature (see
https://docs.google.com/document/d/1Ln57_v6_4RmuuvtWnpsfBOUeDFrPsYNFW13dwuQ8UD8/edit?usp=sharing
for details). We only need this setting to be available to layout tests until
the feature is fully-baked, then we intend to remove this setting and use the
already-existing "acceleratedCompositingForOverflowScrollEnabled" in its place.

R=jchaffraix@chromium.org, vollick@chromium.org

BUG=254406

Review URL: https://codereview.chromium.org/17717002

git-svn-id: svn://svn.chromium.org/blink/trunk@153252 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove IDBDatabaseError

R=abarth@chromium.org, arv@chromium.org
BUG=252395

Review URL: https://codereview.chromium.org/17949004

git-svn-id: svn://svn.chromium.org/blink/trunk@153253 bbb929c8-8fbe-4397-9dbb-9b2b20218538