[Windows] One TimeTicks clock: efficient/reliable high-res, with low-res fallback.

ui/gfx/frame_time.h

 // Copyright 2013 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 UI_GFX_FRAME_TIME_H
 #define UI_GFX_FRAME_TIME_H
 
 #include "base/time/time.h"
 #include "base/logging.h"
 
 namespace gfx {
 
 // FrameTime::Now() should be used to get timestamps with a timebase that
 // is consistent across the graphics stack.
 class FrameTime {
  public:
   static base::TimeTicks Now() {
-    if (TimestampsAreHighRes())
-      return base::TimeTicks::HighResNow();
     return base::TimeTicks::Now();
   }
 
 #if defined(OS_WIN)
   static base::TimeTicks FromQPCValue(LONGLONG qpc_value) {
     DCHECK(TimestampsAreHighRes());
     return base::TimeTicks::FromQPCValue(qpc_value);
   }
 #endif
 
   static bool TimestampsAreHighRes() {
 #if defined(OS_WIN)
-    return base::TimeTicks::IsHighResClockWorking();
+    return base::TimeTicks::IsHighResolution();

[jamesr, 2015/01/08 20:31:54]

imo you should just delete this, it's not producing anything useful

[brianderson, 2015/01/08 21:10:36]

Opened a bug to remove the whole gfx::FrameTime class:
https://code.google.com/p/chromium/issues/detail?id=447329

[miu, 2015/01/08 22:16:00]

What do you mean by "delete this?"  Are you referring to this method, or the
whole FrameTime class?

Either way, I'd prefer to follow-up with this in a later clean-up change.  (I've
already been maintaining a TODO list to track several other clean-up items
resulting from this change.)

[miu, 2015/01/08 22:16:00]

Acknowledged.

 #else
+    // TODO(miu): Mac/Linux always provide high-resolution timestamps.  Consider
+    // returning base::TimeTicks::IsHighResolution() for all platforms.
     return false;
 #endif
   }
 };
 
 }
 
 #endif // UI_GFX_FRAME_TIME_H