Oilpan: Prepare moving HTMLImageElement to oilpan.

BUG=357163

Review URL: https://codereview.chromium.org/290333004

git-svn-id: svn://svn.chromium.org/blink/trunk@174517 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Auto-rebaseline for r174496

http://src.chromium.org/viewvc/blink?view=revision&revision=174496

BUG=376052
TBR=kbr@chromium.org

Review URL: https://codereview.chromium.org/296743008

git-svn-id: svn://svn.chromium.org/blink/trunk@174518 bbb929c8-8fbe-4397-9dbb-9b2b20218538