Implement Chromium side of MediaKeys.isTypeSupported().

content/renderer/renderer_webkitplatformsupport_impl.h

Index: content/renderer/renderer_webkitplatformsupport_impl.h
diff --git a/content/renderer/renderer_webkitplatformsupport_impl.h b/content/renderer/renderer_webkitplatformsupport_impl.h
index 462186ca94286c2a0292924ad7048e0bb0a0fcf8..03176a2a104c7b3bab0046c510b26e8e12d248e1 100644
--- a/content/renderer/renderer_webkitplatformsupport_impl.h
+++ b/content/renderer/renderer_webkitplatformsupport_impl.h
@@ -93,6 +93,12 @@ class CONTENT_EXPORT RendererWebKitPlatformSupportImpl
       unsigned key_size_index,
       const blink::WebString& challenge,
       const blink::WebURL& url);
+  virtual blink::WebContentDecryptionModule::KeySystemSupportedResult
+      isKeySystemSupported(const blink::WebString& key_system,
+                           const blink::WebString& init_data_type,
+                           const blink::WebString& container,
+                           const blink::WebString& codecs,
+                           const blink::WebString& capability);
   virtual void getPluginList(bool refresh,
                              blink::WebPluginListBuilder* builder);
   virtual blink::WebPublicSuffixList* publicSuffixList();