Inherit EventTarget interface instead of duplicating its code

Source/modules/mediasource/SourceBufferList.idl

Index: Source/modules/mediasource/SourceBufferList.idl
diff --git a/Source/modules/mediasource/SourceBufferList.idl b/Source/modules/mediasource/SourceBufferList.idl
index 8c229657ccd96be40c5f6ad764a3ea51b38612f2..80f231d08323a5f4de850d09229b6f8d52da390b 100644
--- a/Source/modules/mediasource/SourceBufferList.idl
+++ b/Source/modules/mediasource/SourceBufferList.idl
@@ -31,19 +31,9 @@
 [
     NoInterfaceObject,
     EnabledAtRuntime=mediaSource,
-    EventTarget,
     CallWith=ScriptExecutionContext
-] interface SourceBufferList {
+] interface SourceBufferList : EventTarget {
     readonly attribute unsigned long length;
     getter SourceBuffer item(unsigned long index);
-
-    // 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);
 };