Read compositor VSync information from platform, when possible

ash/display/display_info.cc

Index: ash/display/display_info.cc
diff --git a/ash/display/display_info.cc b/ash/display/display_info.cc
index d35f0fc0329895e10544afb84d9f64d7bdb6d190..aa04ef161bddb98c16ac814ec91331cafad2aa0b 100644
--- a/ash/display/display_info.cc
+++ b/ash/display/display_info.cc
@@ -23,10 +23,12 @@
 namespace ash {
 namespace internal {
 
-Resolution::Resolution(const gfx::Size& size, bool interlaced)
-    : size(size),
-      interlaced(interlaced) {
-}
+Resolution::Resolution() : refresh_rate(0.0f), interlaced(false) {}
+
+Resolution::Resolution(const gfx::Size& size,
+                       float refresh_rate,
+                       bool interlaced)
+    : size(size), refresh_rate(refresh_rate), interlaced(interlaced) {}
 
 // satic
 DisplayInfo DisplayInfo::CreateFromSpec(const std::string& spec) {
@@ -112,8 +114,14 @@ DisplayInfo DisplayInfo::CreateFromSpecWithID(const std::string& spec,
     for (size_t i = 0; i < count; ++i) {
       std::string resolution = parts[i];
       int width, height;
-      if (sscanf(resolution.c_str(), "%dx%d", &width, &height) == 2)
-        resolutions.push_back(Resolution(gfx::Size(width, height), false));
+      float refresh_rate = 0.0f;
+      if (sscanf(resolution.c_str(),
+                 "%dx%d%%%f",
+                 &width,
+                 &height,
+                 &refresh_rate) >= 2)
+        resolutions.push_back(
+            Resolution(gfx::Size(width, height), refresh_rate, false));
     }
   }
 
@@ -239,9 +247,19 @@ gfx::Insets DisplayInfo::GetOverscanInsetsInPixel() const {
 
 std::string DisplayInfo::ToString() const {
   int rotation_degree = static_cast<int>(rotation_) * 90;
+  std::string resolutions;
+  std::vector<Resolution>::const_iterator iter;
+  for (iter = resolutions_.begin(); iter != resolutions_.end(); ++iter) {
+    base::StringAppendF(&resolutions,
+                        "(%dx%d@%f%c), ",
+                        iter->size.width(),
+                        iter->size.height(),
+                        iter->refresh_rate,
+                        iter->interlaced ? 'I' : 'P');
+  }
   return base::StringPrintf(
       "DisplayInfo[%lld] native bounds=%s, size=%s, scale=%f, "
-      "overscan=%s, rotation=%d, ui-scale=%f, touchscreen=%s",
+      "overscan=%s, rotation=%d, ui-scale=%f, touchscreen=%s, resolutions=[%s]",
       static_cast<long long int>(id_),
       bounds_in_native_.ToString().c_str(),
       size_in_pixel_.ToString().c_str(),
@@ -249,9 +267,12 @@ std::string DisplayInfo::ToString() const {
       overscan_insets_in_dip_.ToString().c_str(),
       rotation_degree,
       configured_ui_scale_,
-      touch_support_ == gfx::Display::TOUCH_SUPPORT_AVAILABLE ? "yes" :
-      touch_support_ == gfx::Display::TOUCH_SUPPORT_UNAVAILABLE ? "no" :
-      "unknown");
+      touch_support_ == gfx::Display::TOUCH_SUPPORT_AVAILABLE
+          ? "yes"
+          : touch_support_ == gfx::Display::TOUCH_SUPPORT_UNAVAILABLE
+                ? "no"
+                : "unknown",
+      resolutions.c_str());
 }
 
 std::string DisplayInfo::ToFullString() const {