[DevTools] Use requestAnimationFrame to synchronize screen update with inspected page resize.

Using requestAnimationFrame may postpone resizing inspected page
until frontend UI has updated.

BUG=331028

Review URL: https://codereview.chromium.org/133773005

git-svn-id: svn://svn.chromium.org/blink/trunk@165001 bbb929c8-8fbe-4397-9dbb-9b2b20218538