[Signin Error Dialog] (3/3) Added the triggering code

chrome/browser/ui/webui/signin/signin_error_handler.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_UI_WEBUI_SIGNIN_SIGNIN_ERROR_HANDLER_H_
+#define CHROME_BROWSER_UI_WEBUI_SIGNIN_SIGNIN_ERROR_HANDLER_H_
+
+#include <string>
+
+#include "base/macros.h"
+#include "content/public/browser/web_ui_message_handler.h"
+
+class Browser;
+class ProfileAttributesEntry;
+
+namespace base {
+class ListValue;
+}
+
+class SigninErrorHandler : public content::WebUIMessageHandler {
+ public:
+  SigninErrorHandler() : duplicate_profile_entry_(nullptr) {}
+  ~SigninErrorHandler() override {}
+
+  // content::WebUIMessageHandler:
+  void RegisterMessages() override;
+
+  // Sets the existing profile entry that has the same username used for signin.
+  // This function is called when the signin error is a duplicate account error.
+  void set_duplicate_profile_entry(
+      const ProfileAttributesEntry* duplicate_profile_entry);
+
+ protected:
+  // Handles "switch" message from the page. No arguments.
+  // This message is sent when the user switches to the existing profile of the
+  // same username used for signin.
+  virtual void HandleSwitch(const base::ListValue* args);

[anthonyvd, 2016/08/22 14:58:46]

Can you make this function name a bit more descriptive? Something like
HandleSwitchToExistingProfile is easier to read at call sites even if it's
longer.

[Jane, 2016/08/22 20:48:31]

Done.

+
+  // Handles "confirm" message from the page. No arguments.
+  // This message is sent when the user acknowledges the signin error.
+  virtual void HandleConfirm(const base::ListValue* args);
+
+  // Handles "learnMore" message from the page. No arguments.
+  // This message is sent when the user clicks on the "Learn more" link in the
+  // signin error dialog, which closes the dialog and takes the user to the
+  // Chrome Help page about fixing sync problems.
+  virtual void HandleLearnMore(const base::ListValue* args);
+
+  // Handles the web ui message sent when the html content is done being laid
+  // out and it's time to resize the native view hosting it to fit. |args| is
+  // a single integer value for the height the native view should resize to.
+  virtual void HandleInitializedWithSize(const base::ListValue* args);
+
+  Browser* GetDesktopBrowser();
+  void CloseDialog();
+
+ private:
+  const ProfileAttributesEntry* duplicate_profile_entry_;
+
+  DISALLOW_COPY_AND_ASSIGN(SigninErrorHandler);
+};
+
+#endif  // CHROME_BROWSER_UI_WEBUI_SIGNIN_SIGNIN_ERROR_HANDLER_H_