Add a JavaScript dialog tab helper.

chrome/browser/ui/javascript_dialogs/javascript_dialog_tab_helper.h

Index: chrome/browser/ui/javascript_dialogs/javascript_dialog_tab_helper.h
diff --git a/chrome/browser/ui/javascript_dialogs/javascript_dialog_tab_helper.h b/chrome/browser/ui/javascript_dialogs/javascript_dialog_tab_helper.h
new file mode 100644
index 0000000000000000000000000000000000000000..24a5e10140344864ef30899db4585b8985c6d7d3
--- /dev/null
+++ b/chrome/browser/ui/javascript_dialogs/javascript_dialog_tab_helper.h
@@ -0,0 +1,46 @@
+// 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_JAVASCRIPT_DIALOGS_JAVASCRIPT_DIALOG_TAB_HELPER_H_
+#define CHROME_BROWSER_UI_JAVASCRIPT_DIALOGS_JAVASCRIPT_DIALOG_TAB_HELPER_H_
+
+#include "base/macros.h"
+#include "content/public/browser/javascript_dialog_manager.h"
+#include "content/public/browser/web_contents_observer.h"
+#include "content/public/browser/web_contents_user_data.h"
+
+class JavaScriptDialogTabHelper
+    : public content::WebContentsObserver,
+      public content::JavaScriptDialogManager,
+      public content::WebContentsUserData<JavaScriptDialogTabHelper> {
+ public:
+  explicit JavaScriptDialogTabHelper(content::WebContents* web_contents);
+  ~JavaScriptDialogTabHelper() override;
+
+  // JavaScriptDialogManager:
+  void RunJavaScriptDialog(content::WebContents* web_contents,
+                           const GURL& origin_url,
+                           content::JavaScriptMessageType message_type,
+                           const base::string16& message_text,
+                           const base::string16& default_prompt_text,
+                           const DialogClosedCallback& callback,
+                           bool* did_suppress_message) override;
+  void RunBeforeUnloadDialog(content::WebContents* web_contents,
+                             bool is_reload,
+                             const DialogClosedCallback& callback) override;
+  bool HandleJavaScriptDialog(content::WebContents* web_contents,
+                              bool accept,
+                              const base::string16* prompt_override) override;
+  void CancelActiveAndPendingDialogs(
+      content::WebContents* web_contents) override;
+  void ResetDialogState(content::WebContents* web_contents) override;
+  void WebContentsDestroyed() override;
+
+ private:
+  friend class content::WebContentsUserData<JavaScriptDialogTabHelper>;
+
+  DISALLOW_COPY_AND_ASSIGN(JavaScriptDialogTabHelper);
+};
+
+#endif  // CHROME_BROWSER_UI_JAVASCRIPT_DIALOGS_JAVASCRIPT_DIALOG_TAB_HELPER_H_