Code:   TestJavaScriptDialogManager()
       : is_fullscreen_(false), message_loop_runner_(new MessageLoopRunner) {}

Commit Message: If a page shows a popup, end fullscreen.

This was implemented in Blink r159834, but it is susceptible
to a popup/fullscreen race. This CL reverts that implementation
and re-implements it in WebContents.

BUG=752003
TEST=WebContentsImplBrowserTest.PopupsFromJavaScriptEndFullscreen

Change-Id: Ia345cdeda273693c3231ad8f486bebfc3d83927f
Reviewed-on: https://chromium-review.googlesource.com/606987
Commit-Queue: Avi Drissman <avi@chromium.org>
Reviewed-by: Charlie Reis <creis@chromium.org>
Reviewed-by: Philip Jägenstedt <foolip@chromium.org>
Cr-Commit-Position: refs/heads/master@{#498171}
CWE ID: CWE-20
  TestJavaScriptDialogManager()
  TestWCDelegateForDialogsAndFullscreen()
       : is_fullscreen_(false), message_loop_runner_(new MessageLoopRunner) {}
