cc: Use HighResNow as timebase if it is fast and reliable

ui/compositor/layer_animator.cc

Index: ui/compositor/layer_animator.cc
diff --git a/ui/compositor/layer_animator.cc b/ui/compositor/layer_animator.cc
index c287574bbb8e1caa9333e9b3df309a2b612efa28..dd727a6c549458e3e9abbc326ec85aa7de2b0d98 100644
--- a/ui/compositor/layer_animator.cc
+++ b/ui/compositor/layer_animator.cc
@@ -8,12 +8,14 @@
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "cc/animation/animation_id_provider.h"
+#include "cc/output/begin_frame_args.h"
 #include "ui/compositor/compositor.h"
 #include "ui/compositor/layer.h"
 #include "ui/compositor/layer_animation_delegate.h"
 #include "ui/compositor/layer_animation_observer.h"
 #include "ui/compositor/layer_animation_sequence.h"
 #include "ui/gfx/animation/animation_container.h"
+#include "ui/gfx/frame_time.h"
 
 #define SAFE_INVOKE_VOID(function, running_anim, ...) \
     if (running_anim.is_sequence_alive()) \
@@ -177,7 +179,7 @@ void LayerAnimator::StartTogether(
     if (GetAnimationContainer()->is_running())
       last_step_time_ = GetAnimationContainer()->last_tick_time();
     else
-      last_step_time_ = base::TimeTicks::Now();
+      last_step_time_ = gfx::FrameTime::Now();
   }
 
   // Collect all the affected properties.
@@ -768,7 +770,7 @@ bool LayerAnimator::StartSequenceImmediately(LayerAnimationSequence* sequence) {
   else if (GetAnimationContainer()->is_running())
     start_time = GetAnimationContainer()->last_tick_time();
   else
-    start_time = base::TimeTicks::Now();
+    start_time = gfx::FrameTime::Now();
 
   if (!sequence->animation_group_id())
     sequence->set_animation_group_id(cc::AnimationIdProvider::NextGroupId());