Cleanup WebCore/storage stuff that doesn't apply in Blink.

BUG=229746
Review URL: https://codereview.chromium.org/14002002

git-svn-id: svn://svn.chromium.org/blink/trunk@148316 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Ensures GraphicsLayer's background color is set

On Android, the compositor will use the background color to draw
temporarily for tiles whose contents are not ready.

BUG=223697
TEST=existing compositing tests
TEST=RenderLayerBackingTest.GraphicsLayerBackgroundColor

Review URL: https://chromiumcodereview.appspot.com/13800008

git-svn-id: svn://svn.chromium.org/blink/trunk@148317 bbb929c8-8fbe-4397-9dbb-9b2b20218538