Add UseCounters to evaluate usage and risk with upcoming WebVR spec changes.

third_party/WebKit/Source/core/frame/UseCounter.h

 /*
  * Copyright (C) 2012 Google, Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 1467 matching lines @@
     ScrollByWheel = 1848,
     ScheduledActionIgnored = 1849,
     GetCanvas2DContextAttributes = 1850,
     V8HTMLInputElement_Capture_AttributeGetter = 1851,
     V8HTMLInputElement_Capture_AttributeSetter = 1852,
     HTMLMediaElementControlsListAttribute = 1853,
     HTMLMediaElementControlsListNoDownload = 1854,
     HTMLMediaElementControlsListNoFullscreen = 1855,
     HTMLMediaElementControlsListNoRemotePlayback = 1856,
     PointerEventClickRetargetCausedByCapture = 1857,
+    VRDisplayIsConnected = 1858,
+    VRDisplayResetPose = 1859,
+    VRDisplayCapabilitiesHasOrientation = 1860,
+    VRDisplayDisplayName = 1861,
+    VREyeParametersOffset = 1862,
+    VRPoseLinearVelocity = 1863,
+    VRPoseLinearAcceleration = 1864,
+    VRPoseAngularVelocity = 1865,
+    VRPoseAngularAcceleration = 1866,
 
     // Add new features immediately above this line. Don't change assigned
     // numbers of any item, and don't reuse removed slots.
     // Also, run update_use_counter_feature_enum.py in
     // chromium/src/tools/metrics/histograms/ to update the UMA mapping.
     NumberOfFeatures,  // This enum value must be last.
   };
 
   // An interface to observe UseCounter changes. Note that this is never
   // notified when the counter is disabled by |m_muteCount| or
@@ skipping 89 matching lines @@
     // Tracks what features/properties need to be reported to the legacy
     // histograms.
     BitVector m_featureBits;
     BitVector m_CSSBits;
   } m_legacyCounter;
 };
 
 }  // namespace blink
 
 #endif  // UseCounter_h