Report correct touch hit rects when
RuntimeEnabledFeatures::overlayFullscreenVideoEnabled is true and have a touch
handler on the document or body.

We had an optimization in the cc touch hit rect calculation that if there was a
handler on the document or body then we'd short circuit the computation and
report a single rect at the root layer covering the whole page. Now when making
an HTML5 video element fullscreen with this flag turned on the
RenderLayerCompositor removes the root cc::layer and reattaches the video layer
causing the compositor to think that there are no handlers registered.


BUG=372314

Review URL: https://codereview.chromium.org/317373007

git-svn-id: svn://svn.chromium.org/blink/trunk@176071 bbb929c8-8fbe-4397-9dbb-9b2b20218538