SyncCompositor: Remove needs_begin_impl_frame_

There is no need to keep a copy of needs_begin_impl_frame_ in subclass
and the super class and it's super confusing too. Just remove it.

Also skip cc::OutputSurface::SetNeedsBeginFrame since sync compositor
does not use framerate controller or retroactive begin frame.

BUG=344087

Review URL: https://codereview.chromium.org/192063002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@256510 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 256510