Inherit EventTarget interface instead of duplicating its code

Source/modules/mediasource/MediaSource.idl

Index: Source/modules/mediasource/MediaSource.idl
diff --git a/Source/modules/mediasource/MediaSource.idl b/Source/modules/mediasource/MediaSource.idl
index d0b407dacc56122c130338be2e158733d0269a35..49d0fd30c7e2d20c5f549763352d47786be23857 100644
--- a/Source/modules/mediasource/MediaSource.idl
+++ b/Source/modules/mediasource/MediaSource.idl
@@ -31,10 +31,9 @@
 [
     EnabledAtRuntime=mediaSource,
     ActiveDOMObject,
-    EventTarget,
     Constructor,
     ConstructorCallWith=ScriptExecutionContext
-] interface MediaSource {
+] interface MediaSource : EventTarget {
     // All the source buffers created by this object.
     readonly attribute SourceBufferList sourceBuffers;
 
@@ -51,13 +50,4 @@
     [RaisesException] void endOfStream([Default=NullString] optional DOMString error);
 
     static boolean isTypeSupported (DOMString type);
-
-    // EventTarget interface
-    void addEventListener(DOMString type,
-                          EventListener listener,
-                          optional boolean useCapture);
-    void removeEventListener(DOMString type,
-                             EventListener listener,
-                             optional boolean useCapture);
-    [RaisesException] boolean dispatchEvent(Event event);
 };