Auto-rebaseline for r178883

http://src.chromium.org/viewvc/blink?view=revision&revision=178883

BUG=392694
TBR=chrishtr@chromium.org

Review URL: https://codereview.chromium.org/417313002

git-svn-id: svn://svn.chromium.org/blink/trunk@178951 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Fix scrollbar damage accumulation issue

Added ScrollableArea::addScrollbarDamage() to accumulate scrollbar
damage rects.

BUG=394833
TEST=fast/repaint/scrollbar-parts.html

Review URL: https://codereview.chromium.org/418483004

git-svn-id: svn://svn.chromium.org/blink/trunk@178952 bbb929c8-8fbe-4397-9dbb-9b2b20218538