Reland 1: "mac: Allow Chrome to hand off its active URL to other devices."

chrome/browser/ui/cocoa/handoff_active_url_observer_delegate.h

+// Copyright 2014 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_COCOA_HANDOFF_ACTIVE_URL_OBSERVER_DELEGATE_H_
+#define CHROME_BROWSER_UI_COCOA_HANDOFF_ACTIVE_URL_OBSERVER_DELEGATE_H_
+
+namespace content {
+class WebContents;
+}
+
+// The delegate for a HandoffActiveURLObserver.
+class HandoffActiveURLObserverDelegate {
+ public:
+  // Called when:
+  //   1. The most recently focused browser changes.
+  //   2. The active tab of the browser changes.
+  //   3. After a navigation of the web contents of the active tab.
+  // |web_contents| is the WebContents whose VisibleURL is considered the
+  // "Active URL" of Chrome.
+  virtual void HandoffActiveURLChanged(content::WebContents* web_contents) = 0;
+
+ protected:
+  virtual ~HandoffActiveURLObserverDelegate(){};
+};
+
+#endif  // CHROME_BROWSER_UI_COCOA_HANDOFF_ACTIVE_URL_OBSERVER_DELEGATE_H_