Implement Chromium side of MediaKeys.isTypeSupported().

content/renderer/media/webcontentdecryptionmodule_impl.h

Index: content/renderer/media/webcontentdecryptionmodule_impl.h
diff --git a/content/renderer/media/webcontentdecryptionmodule_impl.h b/content/renderer/media/webcontentdecryptionmodule_impl.h
index 2619e5610b3eeea3a0ca232bd018536aac3a85e5..8b22a41df04545610236aed3789242c80dc3ea66 100644
--- a/content/renderer/media/webcontentdecryptionmodule_impl.h
+++ b/content/renderer/media/webcontentdecryptionmodule_impl.h
@@ -44,6 +44,13 @@ class WebContentDecryptionModuleImpl
       const blink::WebSecurityOrigin& security_origin,
       const base::string16& key_system);
 
+  static 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 ~WebContentDecryptionModuleImpl();
 
   // Returns the Decryptor associated with this CDM. May be NULL if no