Move {Resolve|Reject}JavascriptCallback helpers in WebUIMessageHandler.

content/public/browser/web_ui_message_handler.h

Index: content/public/browser/web_ui_message_handler.h
diff --git a/content/public/browser/web_ui_message_handler.h b/content/public/browser/web_ui_message_handler.h
index ed0117931f59bc8cc8db1b135a2c606aea0c2015..b088c07030cc7b3a87d807f556baea3ab963a11e 100644
--- a/content/public/browser/web_ui_message_handler.h
+++ b/content/public/browser/web_ui_message_handler.h
@@ -77,6 +77,18 @@ class CONTENT_EXPORT WebUIMessageHandler {
   // to deregister or disabled observers that push JavaScript calls to the page.
   virtual void OnJavascriptDisallowed() {}
 
+  // Helper method for responding to JS requests initiated with
+  // cr.sendWithPromise(), for the case where the returned promise should be
+  // resolved (request succeeded).
+  void ResolveJavascriptCallback(const base::Value& callback_id,
+                                 const base::Value& response);
+
+  // Helper method for responding to JS requests initiated with
+  // cr.sendWithPromise(), for the case where the returned promise should be
+  // rejected (request failed).
+  void RejectJavascriptCallback(const base::Value& callback_id,
+                                const base::Value& response);
+
   // Call a Javascript function by sending its name and arguments down to
   // the renderer.  This is asynchronous; there's no way to get the result
   // of the call, and should be thought of more like sending a message to