Read compositor VSync information from platform, when possible

ash/display/display_manager.cc

Index: ash/display/display_manager.cc
diff --git a/ash/display/display_manager.cc b/ash/display/display_manager.cc
index 9bb154e19089735fb0906fbb355c910ba4ccf108..776a352fb381004157b771424d169ce06e7721c5 100644
--- a/ash/display/display_manager.cc
+++ b/ash/display/display_manager.cc
@@ -452,12 +452,8 @@ void DisplayManager::SetDisplayResolution(int64 display_id,
     LOG(WARNING) << "Unsupported resolution was requested:"
                  << resolution.ToString();
     return;
-  } else if (iter == resolutions.begin()) {
-    // The best resolution was set, so forget it.
-    resolutions_.erase(display_id);
-  } else {
-    resolutions_[display_id] = resolution;
   }
+  resolutions_[display_id] = *iter;
 #if defined(OS_CHROMEOS) && defined(USE_X11)
   if (base::SysInfo::IsRunningOnChromeOS())
     Shell::GetInstance()->output_configurator()->ScheduleConfigureOutputs();
@@ -469,7 +465,8 @@ void DisplayManager::RegisterDisplayProperty(
     gfx::Display::Rotation rotation,
     float ui_scale,
     const gfx::Insets* overscan_insets,
-    const gfx::Size& resolution_in_pixels) {
+    const gfx::Size& resolution_in_pixels,
+    float refresh_rate) {
   if (display_info_.find(display_id) == display_info_.end()) {
     display_info_[display_id] =
         DisplayInfo(display_id, std::string(""), false);
@@ -481,18 +478,21 @@ void DisplayManager::RegisterDisplayProperty(
     display_info_[display_id].set_configured_ui_scale(ui_scale);
   if (overscan_insets)
     display_info_[display_id].SetOverscanInsets(*overscan_insets);
-  if (!resolution_in_pixels.IsEmpty())
-    resolutions_[display_id] = resolution_in_pixels;
+  if (!resolution_in_pixels.IsEmpty()) {
+    resolutions_[display_id] =
+        Resolution(resolution_in_pixels, refresh_rate, false);
+  }
 }
 
 bool DisplayManager::GetSelectedResolutionForDisplayId(
     int64 id,
-    gfx::Size* resolution_out) const {
-  std::map<int64, gfx::Size>::const_iterator iter =
-      resolutions_.find(id);
+    gfx::Size* resolution_out,
+    float* refresh_rate_out) const {
+  std::map<int64, Resolution>::const_iterator iter = resolutions_.find(id);
   if (iter == resolutions_.end())
     return false;
-  *resolution_out = iter->second;
+  *resolution_out = iter->second.size;
+  *refresh_rate_out = iter->second.refresh_rate;
   return true;
 }
 
@@ -575,10 +575,10 @@ void DisplayManager::OnNativeDisplaysChanged(
                      resolutions.end(),
                      ResolutionMatcher(resolution));
     // Update the actual resolution selected as the resolution request may fail.
-    if (resolution_iter == resolutions.begin())
+    if (resolution_iter != resolutions.end())
+      resolutions_[iter->id()] = *resolution_iter;
+    else
       resolutions_.erase(iter->id());
-    else if (resolutions_.find(iter->id()) != resolutions_.end())
-      resolutions_[iter->id()] = resolution;
   }
   if (HasInternalDisplay() &&
       !internal_display_connected &&
@@ -659,7 +659,7 @@ void DisplayManager::UpdateDisplays(
       non_desktop_display_ =
           CreateDisplayFromDisplayInfoById(non_desktop_display_id);
       ++new_info_iter;
-      // Remove existing external dispaly if it is going to be used as
+      // Remove existing external display if it is going to be used as
       // non desktop.
       if (curr_iter != displays_.end() &&
           curr_iter->id() == non_desktop_display_id) {