Implement DataCue interface.

Source/core/html/track/TextTrackCue.h

Index: Source/core/html/track/TextTrackCue.h
diff --git a/Source/core/html/track/TextTrackCue.h b/Source/core/html/track/TextTrackCue.h
index fc9f9407e9430a93959f29ac38190513e9f3511a..ddfaa74ab451582d2e2355be76ae5097968b03be 100644
--- a/Source/core/html/track/TextTrackCue.h
+++ b/Source/core/html/track/TextTrackCue.h
@@ -77,13 +77,16 @@ public:
     bool isActive();
     void setIsActive(bool);
 
-    virtual void updateDisplay(const IntSize& videoSize, HTMLDivElement& container) = 0;
+    virtual void updateDisplay(const IntSize& videoSize, HTMLDivElement& container) { };
 
     // FIXME: Consider refactoring to eliminate or merge the following three members.
     // https://code.google.com/p/chromium/issues/detail?id=322434
-    virtual void updateDisplayTree(double movieTime) = 0;
-    virtual void removeDisplayTree() = 0;
-    virtual void notifyRegionWhenRemovingDisplayTree(bool notifyRegion) = 0;
+    virtual void updateDisplayTree(double movieTime) { };
+    virtual void removeDisplayTree() { };
+    virtual void notifyRegionWhenRemovingDisplayTree(bool notifyRegion) { };
+
+    enum CueType { WebVTT, Data };
+    virtual CueType cueType() const = 0;

[philipj_slow, 2014/04/04 14:54:33]

isVTTCue would be more in line with how the Node hierachy type testing/casting
works.

[Brendan Long, 2014/04/04 15:07:22]

So, remove CueType, and add a 'bool isVTTCue()'? Do we also want a 'bool
isDataCue()', or should we just assume that anything that isn't a VTTCue is a
DataCue?

 
     virtual const AtomicString& interfaceName() const OVERRIDE;