Remove MEDIA_SOURCE feature define.

Source/WebCore/Modules/mediasource/MediaSource.idl

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 11 matching lines @@
  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
  
 [
-    Conditional=MEDIA_SOURCE,
     V8EnabledAtRuntime=mediaSource,
     ActiveDOMObject,
     EventTarget,
     Constructor,
     CallWith=ScriptExecutionContext
 ] interface MediaSource {
     // All the source buffers created by this object.
     readonly attribute SourceBufferList sourceBuffers;
 
     // Subset of sourceBuffers that provide data for the selected/enabled tracks.
@@ skipping 15 matching lines @@
     void addEventListener(in DOMString type,
                           in EventListener listener,
                           in [Optional] boolean useCapture);
     void removeEventListener(in DOMString type,
                              in EventListener listener,
                              in [Optional] boolean useCapture);
     boolean dispatchEvent(in Event event)
         raises(EventException);
 };