Read compositor VSync information from platform, when possible

ui/gl/sync_control_vsync_provider.cc

 // 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.
 
 #include "ui/gl/sync_control_vsync_provider.h"
 
 #include <math.h>
 
 #include "base/logging.h"
 #include "base/time/time.h"
@@ skipping 107 matching lines @@
   if (last_computed_intervals_.size() == 2) {
     const base::TimeDelta& old_interval = last_computed_intervals_.front();
     const base::TimeDelta& new_interval = last_computed_intervals_.back();
 
     double relative_change =
         fabs(old_interval.InMillisecondsF() - new_interval.InMillisecondsF()) /
         new_interval.InMillisecondsF();
     if (relative_change < kRelativeIntervalDifferenceThreshold) {
       if (new_interval.InMicroseconds() < kMinVsyncIntervalUs ||
           new_interval.InMicroseconds() > kMaxVsyncIntervalUs) {
-        LOG(FATAL) << "Calculated bogus refresh interval of "
-                   << new_interval.InMicroseconds() << " us. "
-                   << "Last time base of " << last_timebase_.ToInternalValue()
-                   << " us. "
-                   << "Current time base of " << timebase.ToInternalValue()
-                   << " us. "
-                   << "Last media stream count of "
-                   << last_media_stream_counter_ << ". "
-                   << "Current media stream count of " << media_stream_counter
-                   << ".";
+#if defined(USE_ASH)
+        // On ash platforms (ChromeOS essentially), the real refresh interval is
+        // queried from XRandR, regardless of the value calculated here, and
+        // this value is overriden by ui::CompositorVSyncManager.  The log
+        // should not be fatal in this case. Reconsider all this when XRandR
+        // support is added to non-ash platforms.
+        // http://crbug.com/340851
+        LOG(ERROR)
+#else
+        LOG(FATAL)
+#endif  // USE_ASH
+            << "Calculated bogus refresh interval="
+            << new_interval.InMicroseconds()
+            << " us., last_timebase_=" << last_timebase_.ToInternalValue()
+            << " us., timebase=" << timebase.ToInternalValue()
+            << " us., last_media_stream_counter_=" << last_media_stream_counter_
+            << ", media_stream_counter=" << media_stream_counter;
       } else {
         last_good_interval_ = new_interval;
       }
     }
   }
 
   last_timebase_ = timebase;
   last_media_stream_counter_ = media_stream_counter;
   callback.Run(timebase, last_good_interval_);
 #endif  // defined(OS_LINUX)
 }
 
 }  // namespace gfx