cc: Use HighResNow as timebase if it is fast and reliable

ui/gl/gl_surface_win.cc

 // 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.
 
 #include "ui/gl/gl_surface.h"
 
 #include <dwmapi.h>
 
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/win/windows_version.h"
 #include "third_party/mesa/src/include/GL/osmesa.h"
+#include "ui/gfx/frame_time.h"
 #include "ui/gl/gl_bindings.h"
 #include "ui/gl/gl_implementation.h"
 #include "ui/gl/gl_surface_egl.h"
 #include "ui/gl/gl_surface_osmesa.h"
 #include "ui/gl/gl_surface_stub.h"
 #include "ui/gl/gl_surface_wgl.h"
 
 namespace gfx {
 
 // This OSMesa GL surface can use GDI to swap the contents of the buffer to a
@@ skipping 25 matching lines @@
   virtual ~DWMVSyncProvider() {}
 
   virtual void GetVSyncParameters(const UpdateVSyncCallback& callback) {
     TRACE_EVENT0("gpu", "DWMVSyncProvider::GetVSyncParameters");
     DWM_TIMING_INFO timing_info;
     timing_info.cbSize = sizeof(timing_info);
     HRESULT result = DwmGetCompositionTimingInfo(NULL, &timing_info);
     if (result != S_OK)
       return;
 
-    base::TimeTicks timebase = base::TimeTicks::FromQPCValue(
-        static_cast<LONGLONG>(timing_info.qpcVBlank));
+    base::TimeTicks timebase;
+    // If FrameTime is not high resolution, we do not want to translate the
+    // QPC value provided by DWM into the low-resolution timebase, which
+    // would be error prone and jittery. As a fallback, we assume the timebase
+    // is zero.
+    if (gfx::FrameTime::TimestampsAreHighRes()) {
+      timebase = gfx::FrameTime::FromQPCValue(
+          static_cast<LONGLONG>(timing_info.qpcVBlank));
+    }
+
     // Swap the numerator/denominator to convert frequency to period.
     if (timing_info.rateRefresh.uiDenominator > 0 &&
         timing_info.rateRefresh.uiNumerator > 0) {
       base::TimeDelta interval = base::TimeDelta::FromMicroseconds(
           timing_info.rateRefresh.uiDenominator *
           base::Time::kMicrosecondsPerSecond /
           timing_info.rateRefresh.uiNumerator);
       callback.Run(timebase, interval);
     }
   }
@@ skipping 202 matching lines @@
     }
     case kGLImplementationMockGL:
       return new GLSurfaceStub;
     default:
       NOTREACHED();
       return NULL;
   }
 }
 
 }  // namespace gfx