MD Settings: Add helper method for responding to cr.sendWithPromise.

 - Stop passing the 'cr.webUIResponse' string from JS to C++ and again back to JS.
 - Restricting C++ response to JS to a single argument, since Promises
   can only be resolved with a single argument (this is also more consistent
   with Mojo-based communication).
 - Adding additional test cases.

BUG=580633

Review URL: https://codereview.chromium.org/1635673003

Cr-Commit-Position: refs/heads/master@{#371726}

chrome/browser/resources/settings/appearance_page/appearance_page.js

@@ -124,9 +124,8 @@ Polymer({
   /** @override */
   attached: function() {
     // Query the initial state.
-    cr.sendWithPromise('getResetThemeEnabled').then(function(response) {
-      this.setResetThemeEnabled(response[0]);
-    }.bind(this));
+    cr.sendWithPromise('getResetThemeEnabled').then(
+        this.setResetThemeEnabled.bind(this));
 
     // Set up the change event listener.
     cr.addWebUIListener('reset-theme-enabled-changed',

chrome/browser/ui/webui/settings/appearance_handler.cc

@@ -71,15 +71,12 @@ base::FundamentalValue AppearanceHandler::QueryResetThemeEnabledState() {
 }
 
 void AppearanceHandler::GetResetThemeEnabled(const base::ListValue* args) {
-  CHECK_EQ(2U, args->GetSize());
-
-  std::string callbackFn;
-  CHECK(args->GetString(0, &callbackFn));
-  const base::Value* callbackId;
-  CHECK(args->Get(1, &callbackId));
+  CHECK_EQ(1U, args->GetSize());
+  const base::Value* callback_id;
+  CHECK(args->Get(0, &callback_id));
 
   base::FundamentalValue enabled(QueryResetThemeEnabledState());
-  web_ui()->CallJavascriptFunction(callbackFn, *callbackId, enabled);
+  CallJavascriptCallback(*callback_id, enabled);
 }
 
 }  // namespace settings

chrome/browser/ui/webui/settings/md_settings_ui.cc

@@ -40,6 +40,12 @@ SettingsPageUIHandler::SettingsPageUIHandler() {
 SettingsPageUIHandler::~SettingsPageUIHandler() {
 }
 
+void SettingsPageUIHandler::CallJavascriptCallback(
+    const base::Value& callback_id, const base::Value& response) {
+  // cr.webUIResponse is a global JS function exposed from cr.js.
+  web_ui()->CallJavascriptFunction("cr.webUIResponse", callback_id, response);
+}
+
 MdSettingsUI::MdSettingsUI(content::WebUI* web_ui)
     : content::WebUIController(web_ui) {
   Profile* profile = Profile::FromWebUI(web_ui);

chrome/browser/ui/webui/settings/md_settings_ui.h

@@ -25,6 +25,12 @@ class SettingsPageUIHandler : public content::WebUIMessageHandler {
   // WebUIMessageHandler implementation.
   void RegisterMessages() override {}
 
+ protected:
+  // Helper method for responding to JS requests initiated with
+  // cr.sendWithPromise().
+  void CallJavascriptCallback(const base::Value& callback_id,
+                              const base::Value& response);
+
  private:
   DISALLOW_COPY_AND_ASSIGN(SettingsPageUIHandler);
 };

chrome/test/data/webui/webui_resource_async_browsertest.js

@@ -56,22 +56,39 @@ TEST_F('WebUIResourceAsyncTest', 'SendWithPromise', function() {
     setup(function() {
       // Simulate a WebUI handler that echoes back all parameters passed to it.
       whenChromeSendCalled(CHROME_SEND_NAME).then(function(args) {
-        assertEquals('cr.webUIResponse', args[0]);
-        var globalCallbackArgs = args.slice(1);
-        cr.webUIResponse.apply(null, globalCallbackArgs);
+        cr.webUIResponse.apply(null, args);
       });
     });
 
-    test('sendWithPromise_MultipleArgs', function() {
-      return cr.sendWithPromise(CHROME_SEND_NAME, 'foo', 'bar').then(
+    test('sendWithPromise_ResponseObject', function() {
+      var expectedResponse = {'foo': 'bar'};
+      return cr.sendWithPromise(CHROME_SEND_NAME, expectedResponse).then(
           function(response) {
-            assertEquals(['foo', 'bar'].join(), response.join());
+            assertEquals(
+                JSON.stringify(expectedResponse), JSON.stringify(response));
           });
     });
 
-    test('sendWithPromise_NoArgs', function() {
+    test('sendWithPromise_ResponseArray', function() {
+      var expectedResponse = ['foo', 'bar'];
+      return cr.sendWithPromise(CHROME_SEND_NAME, expectedResponse).then(
+          function(response) {
+            assertEquals(
+                JSON.stringify(expectedResponse), JSON.stringify(response));
+          });
+    });
+
+    test('sendWithPromise_ResponsePrimitive', function() {
+      var expectedResponse = 1234;
+      return cr.sendWithPromise(CHROME_SEND_NAME, expectedResponse).then(
+          function(response) {
+            assertEquals(expectedResponse, response);
+          });
+    });
+
+    test('sendWithPromise_ResponseVoid', function() {
       return cr.sendWithPromise(CHROME_SEND_NAME).then(function(response) {
-        assertEquals([].join(), response.join());
+        assertEquals(undefined, response);
       });
     });
   });

ui/webui/resources/js/cr.js

@@ -331,15 +331,12 @@ var cr = function() {
    * supply any number of other arguments that will be included in the response.
    * @param {string} id The unique ID identifying the Promise this response is
    *     tied to.
-   * @param {...*} var_args Variable number of arguments to be included in the
-   *     response.
+   * @param {*} response The response as sent from C++.
    */
-  function webUIResponse(id, var_args) {
+  function webUIResponse(id, response) {
     var resolverFn = chromeSendResolverMap[id];
     delete chromeSendResolverMap[id];
-    // Promise#resolve accepts only one value, therefore wrapping all arguments
-    // passed from C++ to JS in an array.
-    resolverFn(Array.prototype.slice.call(arguments, 1));
+    resolverFn(response);
   }
 
   /**
@@ -355,7 +352,7 @@ var cr = function() {
     return new Promise(function(resolve, reject) {
       var id = methodName + '_' + createUid();
       chromeSendResolverMap[id] = resolve;
-      chrome.send(methodName, ['cr.webUIResponse', id].concat(args));
+      chrome.send(methodName, [id].concat(args));
     });
   }