Fix RenderWidgetHostViewAura as observer of CompositorVSyncManager

RWHVA needs to deregister itself properly as an observer of
CompositorVSyncManager even if the compositor itself is destroyed.  Do this
properly by keeping a reference to the CompositorVSyncManager.

BUG=343199
TEST=local build, run on desktop Linux, Win7

Review URL: https://codereview.chromium.org/152983004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251017 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251017
Reland 153623004: Remove the unified IO code on the browser

Remove the unified IO code on the browser.

Unified IO is not used any more and it should be removed.

TBR=dalecurtis@chromium.org
BUG=337096
TEST=bots, and nothing breaks.

Review URL: https://codereview.chromium.org/163343002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251018 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251018