Drop kDisableAcceleratedVideoDecode in ContentBrowserTest::SetUp().

ContentBrowserTest calls renderer_main which will set
kDisableAcceleratedVideoDecode through
GpuDataManagerImplPrivate::AppendRendererCommandLine. So setting this flag here
is redundant.

R=fischman@chromium.org
TBR=zmo@chromium.org
BUG=none
TEST=none

Review URL: https://codereview.chromium.org/39413002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@231076 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 231076
Make GetRootWindow() return a Window instead of a RootWindow.

Also adds a typedef from RootWindow to WindowEventDispatcher, the eventual name of this type.
Adds a GetDispatcher() method that crawls up to the root Window and returns the WindowEventDispatcher.

R=sky@chromium.org
http://crbug.com/308843

Review URL: https://codereview.chromium.org/37733003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@231077 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 231077