Remove the dependency on encryptedmedia from HTMLMediaElement.

Source/modules/encryptedmedia/HTMLMediaElementEncryptedMedia.idl

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+partial interface HTMLMediaElement {
+    [RuntimeEnabled=PrefixedEncryptedMedia, RaisesException, MeasureAs=PrefixedMediaGenerateKeyRequest] void webkitGenerateKeyRequest([TreatNullAs=NullString, TreatUndefinedAs=NullString] DOMString keySystem, optional Uint8Array initData);
+    [RuntimeEnabled=PrefixedEncryptedMedia, RaisesException, MeasureAs=PrefixedMediaAddKey] void webkitAddKey([TreatNullAs=NullString, TreatUndefinedAs=NullString] DOMString keySystem, Uint8Array key, optional Uint8Array initData, [Default=NullString] optional DOMString sessionId);
+    [RuntimeEnabled=PrefixedEncryptedMedia, RaisesException, MeasureAs=PrefixedMediaCancelKeyRequest] void webkitCancelKeyRequest([TreatNullAs=NullString, TreatUndefinedAs=NullString] DOMString keySystem, [Default=NullString] optional DOMString sessionId);
+
+    [RuntimeEnabled=PrefixedEncryptedMedia] attribute EventHandler onwebkitkeyadded;
+    [RuntimeEnabled=PrefixedEncryptedMedia] attribute EventHandler onwebkitkeyerror;
+    [RuntimeEnabled=PrefixedEncryptedMedia] attribute EventHandler onwebkitkeymessage;
+    [RuntimeEnabled=PrefixedEncryptedMedia] attribute EventHandler onwebkitneedkey;
+
+    [RuntimeEnabled=EncryptedMedia] readonly attribute MediaKeys mediaKeys;
+    [RuntimeEnabled=EncryptedMedia, RaisesException] void setMediaKeys(MediaKeys mediaKeys);
+    [RuntimeEnabled=EncryptedMedia] attribute EventHandler onneedkey;
+};