Read compositor VSync information from platform, when possible

ash/display/display_info.h

Index: ash/display/display_info.h
diff --git a/ash/display/display_info.h b/ash/display/display_info.h
index ca6f270a9e66163c1dfbcdc54c7f915988731e27..c66855412166dd1072773bebd55d2666edc08672 100644
--- a/ash/display/display_info.h
+++ b/ash/display/display_info.h
@@ -19,9 +19,11 @@ namespace internal {
 // A struct that represents the display's resolution and
 // interlaced info.
 struct ASH_EXPORT Resolution {

[oshima, 2014/01/27 18:53:22]

We probably should rename this to DisplayMode as it has more than resolution
now.

[sheu, 2014/01/28 21:30:42]

Done.

-  Resolution(const gfx::Size& size, bool interlaced);
+  Resolution();
+  Resolution(const gfx::Size& size, float refresh_rate, bool interlaced);
 
   gfx::Size size;
+  float refresh_rate;
   bool interlaced;
 };
 
@@ -47,7 +49,7 @@ class ASH_EXPORT DisplayInfo {
   //   270 degrees (to the 'l'eft).
   // - ui-scale is floating value, e.g. @1.5 or @1.25.
   // - |resolution list| is the list of size that is given in
-  //   |width x height| separated by '|'.
+  //   |width x height [% refresh_rate]| separated by '|'.
   //
   // A couple of examples:
   // "100x100"
@@ -63,9 +65,9 @@ class ASH_EXPORT DisplayInfo {
   // "10+20-300x200/u@1.5"
   //      300x200 window at 10,20 origin. 1x device scale factor.
   //      no overscan. flipped upside-down (180 degree) and 1.5 ui scale.
-  // "200x100#300x200|200x100|100x100"
+  // "200x100#300x200|200x100%59.0|100x100%60"
   //      200x100 window at 0,0 origin, with 3 possible resolutions,
-  //      300x200, 200x100 and 100x100.
+  //      300x200, 200x100 at 59 Hz, and 100x100 at 60 Hz.
   static DisplayInfo CreateFromSpec(const std::string& spec);
 
   // Creates a DisplayInfo from string spec using given |id|.