Inherit EventTarget interface instead of duplicating its code

Source/modules/webaudio/AudioContext.h

Index: Source/modules/webaudio/AudioContext.h
diff --git a/Source/modules/webaudio/AudioContext.h b/Source/modules/webaudio/AudioContext.h
index cde1de85e7244065149bc53872bb32a868f51fad..7cc5f10b65af5e14362f914f598ed48902ca5638 100644
--- a/Source/modules/webaudio/AudioContext.h
+++ b/Source/modules/webaudio/AudioContext.h
@@ -73,7 +73,7 @@ class PeriodicWave;
 // AudioContext is the cornerstone of the web audio API and all AudioNodes are created from it.
 // For thread safety between the audio thread and the main thread, it has a rendering graph locking mechanism.
 
-class AudioContext : public ActiveDOMObject, public ScriptWrappable, public ThreadSafeRefCounted<AudioContext>, public EventTarget {
+class AudioContext : public EventTarget, public ActiveDOMObject, public ScriptWrappable, public ThreadSafeRefCounted<AudioContext> {
 public:
     // Create an AudioContext for rendering to the audio hardware.
     static PassRefPtr<AudioContext> create(Document*);