Add a sizes attribute runtime flag
Add a sizes attribute runtime flag

BUG=357586

Review URL: https://codereview.chromium.org/230973002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@171164 bbb929c8-8fbe-4397-9dbb-9b2b20218538

primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs