Read compositor VSync information from platform, when possible

chromeos/display/output_configurator.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROMEOS_DISPLAY_OUTPUT_CONFIGURATOR_H_
 #define CHROMEOS_DISPLAY_OUTPUT_CONFIGURATOR_H_
 
 #include <map>
 #include <string>
 #include <vector>
@@ skipping 155 matching lines @@
   // Interface for classes that make decisions about which output state
   // should be used.
   class StateController {
    public:
     virtual ~StateController() {}
 
     // Called when displays are detected.
     virtual OutputState GetStateForDisplayIds(
         const std::vector<int64>& display_ids) const = 0;
 
-    // Queries the resolution (|width|x|height|) in pixels
-    // to select output mode for the given display id.
+    // Queries the resolution (|width|x|height|) in pixels and |refresh_rate| in
+    // Hz to select output mode for the given display id.
     virtual bool GetResolutionForDisplayId(int64 display_id,
                                            int* width,
-                                           int* height) const = 0;
+                                           int* height,
+                                           float* refresh_rate) const = 0;

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

Looks like you're not using refresh_rate in output configurator. Do you need
this here?

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

Done.

   };
 
   // Interface for classes that implement software based mirroring.
   class SoftwareMirroringController {
    public:
     virtual ~SoftwareMirroringController() {}
 
     // Called when the hardware mirroring failed.
     virtual void SetSoftwareMirroring(bool enabled) = 0;
   };
@@ skipping 370 matching lines @@
   int casting_session_count_;
 
   DISALLOW_COPY_AND_ASSIGN(OutputConfigurator);
 };
 
 typedef std::vector<OutputConfigurator::OutputSnapshot> OutputSnapshotList;
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_DISPLAY_OUTPUT_CONFIGURATOR_H_