Add Stubbed implementation of WebCDM* interfaces for unprefixed EME APIs.

content/renderer/renderer_webkitplatformsupport_impl.cc

Index: content/renderer/renderer_webkitplatformsupport_impl.cc
diff --git a/content/renderer/renderer_webkitplatformsupport_impl.cc b/content/renderer/renderer_webkitplatformsupport_impl.cc
index cd622f8905ece9225332c3f3a9c99d69a7aa053d..0a73a1c91682287f614df99f02702b20aebb5cf7 100644
--- a/content/renderer/renderer_webkitplatformsupport_impl.cc
+++ b/content/renderer/renderer_webkitplatformsupport_impl.cc
@@ -31,6 +31,7 @@
 #include "content/renderer/hyphenator/hyphenator.h"
 #include "content/renderer/media/media_stream_dependency_factory.h"
 #include "content/renderer/media/renderer_webaudiodevice_impl.h"
+#include "content/renderer/media/renderer_webcdm_impl.h"
 #include "content/renderer/render_thread_impl.h"
 #include "content/renderer/renderer_clipboard_client.h"
 #include "content/renderer/websharedworkerrepository_impl.h"
@@ -731,6 +732,13 @@ RendererWebKitPlatformSupportImpl::createAudioDevice(
 
 //------------------------------------------------------------------------------
 
+WebKit::WebCDM* RendererWebKitPlatformSupportImpl::createCDM(
+    const WebKit::WebString& keySystem) {
+  return RendererWebCDMImpl::create(keySystem);
+}
+
+//------------------------------------------------------------------------------
+
 WebKit::WebString
 RendererWebKitPlatformSupportImpl::signedPublicKeyAndChallengeString(
     unsigned key_size_index,