Revert "Implement FullScreen using top layer."

Reason for revert: Causes several issues when going into/out of fullscreen.

Implement FullScreen using top layer.

This CL is based off of https://codereview.chromium.org/788073004 by jchaffraix@.

  Replace RenderFullscreen with top layer - Take II

  This patch is strongly inspired by
  https://codereview.chromium.org/134753003/
  but is a complete rewrite of the change to:
   - understand why every bits was needed (some were not).
   - better document the differences we have with the
     specification so that we can track and fix them.

  The issue with re-attaching plugins went away due to
  https://codereview.chromium.org/23618022, which moved
  the plugin's lifecycle to the DOM.

  The tests' changes are because fullscreen doesn't center
  by default anymore but stretches the element to the
  viewport's size. Some tests were also not accounting
  for the backdrop and where thus modified.

That change didn't land due to plugin persistence issues. Those issues
should now be resolved and plugins should survive over reattach.

BUG=240576, 246077, 398599, 543946, 543954, 544175
ORIGINAL_CL=https://codereview.chromium.org/1139033006/

Review URL: https://codereview.chromium.org/1363023005

Cr-Commit-Position: refs/heads/master@{#353782}

Review URL: https://codereview.chromium.org/1410833004

Cr-Commit-Position: refs/heads/master@{#355313}
37 files changed