Read compositor VSync information from platform, when possible

ash/display/display_controller.cc

Index: ash/display/display_controller.cc
diff --git a/ash/display/display_controller.cc b/ash/display/display_controller.cc
index 7b7cc5882e5592a336e718a28d2fa3c442bb5215..dabf8d42e7ffd968241cd037abb60861e359ad9b 100644
--- a/ash/display/display_controller.cc
+++ b/ash/display/display_controller.cc
@@ -33,6 +33,7 @@
 #include "ui/aura/window_property.h"
 #include "ui/aura/window_tracker.h"
 #include "ui/compositor/compositor.h"
+#include "ui/compositor/compositor_vsync_manager.h"
 #include "ui/gfx/display.h"
 #include "ui/gfx/screen.h"
 
@@ -119,6 +120,13 @@ void SetDisplayPropertiesOnHostWindow(aura::RootWindow* root,
   scoped_ptr<aura::RootWindowTransformer> transformer(
       internal::CreateRootWindowTransformerForDisplay(root->window(), display));
   root->host()->SetRootWindowTransformer(transformer.Pass());
+
+  internal::DisplayMode mode;
+  if (GetDisplayManager()->GetSelectedModeForDisplayId(display.id(), &mode)) {
+    root->host()->compositor()->vsync_manager()->SetAuthoritativeVSyncInterval(
+        base::TimeDelta::FromMicroseconds(base::Time::kMicrosecondsPerSecond /
+                                          mode.refresh_rate));

[piman, 2014/02/04 04:51:01]

I think there's some cases where refresh_rate could be 0, in which case we
should skip the SetAuthoritativeVSyncInterval altogether.

[sheu, 2014/02/04 22:01:45]

And the div-by-zero.  Done.

+  }
 }
 
 }  // namespace