Reland r165710 "Replace RenderFullScreen with top layer"

It broke browser_test OutOfProcessPPAPITest.Fullscreen by tripping an
assert reached by calling pluginWidget in HTMLPluginElement::detach
which causes a layout. The solution is to get the existing widget
without causing a layout.

Original code review: https://codereview.chromium.org/139743005/

BUG=240576, 246077

Review URL: https://codereview.chromium.org/134753003

git-svn-id: svn://svn.chromium.org/blink/trunk@165904 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Count minor features related to form association.

This CL adds the following counters:
- FormNameAccessForImageElement
  Counts if form.name retuns an IMG elment.
- FormNameAccessForPastNamesMap
  Counts if form.name returns a renamed associated elemnt.
- FormAssociationByParser
  This counts only when the HTML parser associates an element, and it's not a
  descendant of the FORM elemnt.

BUG=none
TEST=none; no behavior changes.

Review URL: https://codereview.chromium.org/136113011

git-svn-id: svn://svn.chromium.org/blink/trunk@165905 bbb929c8-8fbe-4397-9dbb-9b2b20218538