Still permanently disable remoting if stopped by fatal errors, such as mojo pipeline errors, receiver initialization errors, etc.

Chatted with amp@ and johnpallett@ offline and decided to make the behavior consistent for all fallback cases.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/4e722f4ea3de39a305b795ee50d85c0725cdf0ff

commit 4e722f4ea3de39a305b795ee50d85c0725cdf0ff
Author: Xiangjun Zhang <xjz@chromium.org>
Date: Wed Nov 29 20:39:03 2017

Not permanently disable media remoting after fallback due to network

When media remoting is forced back to mirroring due to high frame drop
rate or too slow pacing, the existing logic disables media remoting for
the whole life time of RendererController. This CL re-enables remoting
if the media element stops and later re-starts being the dominant
visible content in the tab.

Bug:  789007 
Change-Id: I85a7f7921b16fa20d3a1aeda8c509367a0184df8
Reviewed-on: https://chromium-review.googlesource.com/792634
Commit-Queue: Xiangjun Zhang <xjz@chromium.org>
Reviewed-by: Xiaohan Wang <xhwang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#520231}
[modify] https://crrev.com/4e722f4ea3de39a305b795ee50d85c0725cdf0ff/media/remoting/renderer_controller.cc
[modify] https://crrev.com/4e722f4ea3de39a305b795ee50d85c0725cdf0ff/media/remoting/renderer_controller.h
[modify] https://crrev.com/4e722f4ea3de39a305b795ee50d85c0725cdf0ff/media/remoting/renderer_controller_unittest.cc