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

cc/trees/single_thread_proxy.cc

Index: cc/trees/single_thread_proxy.cc
diff --git a/cc/trees/single_thread_proxy.cc b/cc/trees/single_thread_proxy.cc
index 634c3bc8b3cd3625e91a45c04be69ba89c1754e1..7a5d224ef08901d20f2a03d7c2f8e478a5a617c5 100644
--- a/cc/trees/single_thread_proxy.cc
+++ b/cc/trees/single_thread_proxy.cc
@@ -15,6 +15,7 @@
 #include "cc/trees/blocking_task_runner.h"
 #include "cc/trees/layer_tree_host.h"
 #include "cc/trees/layer_tree_impl.h"
+#include "ui/gfx/frame_time.h"
 
 namespace cc {
 
@@ -59,7 +60,7 @@ bool SingleThreadProxy::CompositeAndReadback(void* pixels, gfx::Rect rect) {
   gfx::Rect device_viewport_damage_rect = rect;
 
   LayerTreeHostImpl::FrameData frame;
-  if (!CommitAndComposite(base::TimeTicks::Now(),
+  if (!CommitAndComposite(gfx::FrameTime::Now(),

[ajuma, 2013/10/17 20:14:56]

We'll also need to fix the other call to CommitAndComposite (from
CompositeImmediately below), which means tracing back to where the time passed
in to CommitAndComposite comes from. I believe RenderWidget::DoDeferredUpdate
and ui::Compositor::Draw are two such places. Also, looking at ui::Compositor,
SchedulerDraw() calls LayerTreeHost::Composite with a TimeTicks::Now().

                           device_viewport_damage_rect,
                           true,  // for_readback
                           &frame))