RuntimeEnabledFeatures::slimmingPaintOffsetCaching

Put paint offset caching code under this condition because we may
enable it for slimming paint v1.

Also add a test for bug 533277, and exclude paint-offset workaround
when paint offset caching is enabled.

BUG=508383,533277

Review URL: https://codereview.chromium.org/1355753008

git-svn-id: svn://svn.chromium.org/blink/trunk@202658 bbb929c8-8fbe-4397-9dbb-9b2b20218538
10 files changed