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

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

Index: Source/core/html/track/vtt/VTTCue.cpp
diff --git a/Source/core/html/track/vtt/VTTCue.cpp b/Source/core/html/track/vtt/VTTCue.cpp
index 83eb98e01169ad78ed13b1dbe813f83e30eecaf8..9e35ca93984e0f2250627ed388732ad25e3719b9 100644
--- a/Source/core/html/track/vtt/VTTCue.cpp
+++ b/Source/core/html/track/vtt/VTTCue.cpp
@@ -555,6 +555,9 @@ void VTTCue::calculateDisplayParameters()
     // 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