[ProtocolHandlers] Add a permission bubble client for RPH requests.

chrome/browser/custom_handlers/protocol_handler_registry.h

Index: chrome/browser/custom_handlers/protocol_handler_registry.h
diff --git a/chrome/browser/custom_handlers/protocol_handler_registry.h b/chrome/browser/custom_handlers/protocol_handler_registry.h
index f43183383635fb9fe3947a5e973227d70febc198..7a7369c22f476f1e09ae2087ccfe1b50df01de68 100644
--- a/chrome/browser/custom_handlers/protocol_handler_registry.h
+++ b/chrome/browser/custom_handlers/protocol_handler_registry.h
@@ -146,6 +146,11 @@ class ProtocolHandlerRegistry : public BrowserContextKeyedService {
   // function returns false the user needs to be prompted for confirmation.
   bool SilentlyHandleRegisterHandlerRequest(const ProtocolHandler& handler);
 
+  // Display the UI request for the site's permission to register a protocol
+  // handler.
+  void RequestPermission(content::WebContents* web_contents,
+                         const ProtocolHandler& handler);
+
   // Called when the user accepts the registration of a given protocol handler.
   void OnAcceptRegisterProtocolHandler(const ProtocolHandler& handler);