cc: Finish frame early if main thread is idle regardless of redraw state

This condition was added originally in this patch:
https://codereview.chromium.org/27200003

That patch was trying to trigger early deadlines when the compositor
thread had work to do but the main thread had aborted.

In a world where we have begin frame acks even when frames aren't
produced, it's worth triggering early deadlines even when the compositor
thread doesn't have any work to do either so that the display compositor
can go ahead and do work earlier.

This is intended as a short-term fix to solve smoothness issues with
surface for video with 30fps videos.  Ideally the DisplayCompositor will
have some followups as well so that one client that is slow to respond
will not cause smoothness issues with another client.

Bug: 874676
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I8b6663570aba7d135c1f211a21c37b1e17d19577
Reviewed-on: https://chromium-review.googlesource.com/1176559
Commit-Queue: enne <enne@chromium.org>
Reviewed-by: Sunny Sachanandani <sunnyps@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583908}

cc/scheduler/scheduler_state_machine.cc

@@ -1123,9 +1123,6 @@ bool SchedulerStateMachine::ShouldTriggerBeginImplFrameDeadlineImmediately()
   if (active_tree_needs_first_draw_)
     return true;
 
-  if (!needs_redraw_)
-    return false;
-
   // This is used to prioritize impl-thread draws when the main thread isn't
   // producing anything, e.g., after an aborted commit. We also check that we
   // don't have a pending tree -- otherwise we should give it a chance to