Add a use counter for VTTCue right-to-left rendering

Source/core/html/track/vtt/VTTCue.cpp

 /*
  * Copyright (c) 2013, Opera Software ASA. 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 537 matching lines @@
     return isLeftToRightDirection(textDirection) ? CSSValueLtr : CSSValueRtl;
 }
 
 void VTTCue::calculateDisplayParameters()
 {
     createVTTNodeTree();
 
     // Steps 10.2, 10.3
     m_displayDirection = determineTextDirection(m_vttNodeTree.get());
 
+    if (m_displayDirection == CSSValueRtl)
+        UseCounter::count(document(), UseCounter::VTTCueRenderRtl);
+
     // 10.4 If the text track cue writing direction is horizontal, then let
     // block-flow be 'tb'. Otherwise, if the text track cue writing direction is
     // vertical growing left, then let block-flow be 'lr'. Otherwise, the text
     // track cue writing direction is vertical growing right; let block-flow be
     // 'rl'.
 
     // The above step is done through the writing direction static map.
 
     // 10.5 Determine the value of maximum size for cue as per the appropriate
     // rules from the following list:
@@ skipping 528 matching lines @@
 
 void VTTCue::trace(Visitor* visitor)
 {
     visitor->trace(m_vttNodeTree);
     visitor->trace(m_cueBackgroundBox);
     visitor->trace(m_displayTree);
     TextTrackCue::trace(visitor);
 }
 
 } // namespace WebCore