Plumb through a setting for using filters as a compositing trigger (ie., always using accelerated filters).

R=jamesr
BUG=237641

Review URL: https://chromiumcodereview.appspot.com/17553009

git-svn-id: svn://svn.chromium.org/blink/trunk@152908 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Reset page scale to 1.0 during enterFullscreen.

Fullscreened elements need to be sized in CSS pixels regardless of the
previous page scale.  This resets page scale to 1.0 when entering
fullscreen and saves/restores it (and the scroll offset which could be
clamped) to return to the original place on the page when exiting.

NOTRY=true
BUG=239291,252310

Review URL: https://chromiumcodereview.appspot.com/16979003

git-svn-id: svn://svn.chromium.org/blink/trunk@152909 bbb929c8-8fbe-4397-9dbb-9b2b20218538