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

The original CL used instance variables in a class extension and automatic
generation of ivars for synthesized properties, features only available on
64-bit builds. The Mac Memory bots are still compiling Chromium in 32-bits.
This reland removes the usage of those features.

> This CL adds the class HandoffManager, which is responsible for interfacing
> with Apple's Handoff APIs. It takes a GURL, and exposes that GURL to Handoff.
>
> This CL adds the class ActiveWebContentsObserver, which is responsible for
> listening to changes to the active browser, the active tab, and the visible
> URL. It notifies its delegate when any of this state might have changed.
>
> AppControllerMac is the delegate of ActiveWebContentsObserver, as well as the
> owner of the HandoffManager. When it receives a delegate callback, it passes an
> updated GURL to the HandoffManager. There is some minimal logic in
> AppControllerMac that prevents URLs from incognito windows from being passed to
> the HandoffManager.
>
> BUG=431051, 438823
> Committed: https://crrev.com/708abc5b0abb5e0916d779bf6d1342fd472a2aa1
> Cr-Commit-Position: refs/heads/master@{#307846}

BUG=431051, 438823
TBR=sky, erikwright, mmenke, avi

Review URL: https://codereview.chromium.org/794853004

Cr-Commit-Position: refs/heads/master@{#308005}

8 files changed, 534 insertions, 2 deletions

diff --git a/chrome/browser/app_controller_mac.h b/chrome/browser/app_controller_mac.h
index 6eb522c..a3f6481 100644
--- a/chrome/browser/app_controller_mac.h
+++ b/chrome/browser/app_controller_mac.h
@@ -22,6 +22,8 @@ class AppControllerProfileObserver;
 class BookmarkMenuBridge;
 class CommandUpdater;
 class GURL;
+class HandoffActiveURLObserverBridge;
+@class HandoffManager;
 class HistoryMenuBridge;
 class Profile;
 @class ProfileMenuController;
@@ -97,6 +99,13 @@ class WorkAreaWatcherObserver;
 
   // Displays a notification when quitting while apps are running.
   scoped_refptr<QuitWithAppsController> quitWithAppsController_;
+
+  // Responsible for maintaining all state related to the Handoff feature.
+  base::scoped_nsobject<HandoffManager> handoffManager_;
+
+  // Observes changes to the active URL.
+  scoped_ptr<HandoffActiveURLObserverBridge>
+      handoff_active_url_observer_bridge_;
 }
 
 @property(readonly, nonatomic) BOOL startupComplete;
diff --git a/chrome/browser/app_controller_mac.mm b/chrome/browser/app_controller_mac.mm
index 2e2dfe5..604f217 100644
--- a/chrome/browser/app_controller_mac.mm
+++ b/chrome/browser/app_controller_mac.mm
@@ -63,6 +63,7 @@
 #import "chrome/browser/ui/cocoa/confirm_quit.h"
 #import "chrome/browser/ui/cocoa/confirm_quit_panel_controller.h"
 #import "chrome/browser/ui/cocoa/encoding_menu_controller_delegate_mac.h"
+#include "chrome/browser/ui/cocoa/handoff_active_url_observer_bridge.h"
 #import "chrome/browser/ui/cocoa/history_menu_bridge.h"
 #include "chrome/browser/ui/cocoa/last_active_browser_cocoa.h"
 #import "chrome/browser/ui/cocoa/profiles/profile_menu_controller.h"
@@ -83,6 +84,7 @@
 #include "chrome/common/url_constants.h"
 #include "chrome/grit/chromium_strings.h"
 #include "chrome/grit/generated_resources.h"
+#include "components/handoff/handoff_manager.h"
 #include "components/handoff/handoff_utility.h"
 #include "components/signin/core/browser/signin_manager.h"
 #include "components/signin/core/common/profile_management_switches.h"
@@ -209,9 +211,10 @@ bool IsProfileSignedOut(Profile* profile) {
   return cache.ProfileIsSigninRequiredAtIndex(profile_index);
 }
 
-}  // anonymous namespace
+}  // namespace
+
+@interface AppController () <HandoffActiveURLObserverBridgeDelegate>
 
-@interface AppController (Private)
 - (void)initMenuState;
 - (void)initProfileMenu;
 - (void)updateConfirmToQuitPrefMenuItem:(NSMenuItem*)item;
@@ -240,6 +243,25 @@ bool IsProfileSignedOut(Profile* profile) {
 // this method is called, and that tab is the NTP, then this method closes the
 // NTP after all the |urls| have been opened.
 - (void)openUrlsReplacingNTP:(const std::vector<GURL>&)urls;
+
+// Whether instances of this class should use the Handoff feature.
+- (BOOL)shouldUseHandoff;
+
+// This method passes |handoffURL| to |handoffManager_|.
+- (void)passURLToHandoffManager:(const GURL&)handoffURL;
+
+// Lazily creates the Handoff Manager. Updates the state of the Handoff
+// Manager. This method is idempotent. This should be called:
+// - During initialization.
+// - When the current tab navigates to a new URL.
+// - When the active browser changes.
+// - When the active browser's active tab switches.
+// |webContents| should be the new, active WebContents.
+- (void)updateHandoffManager:(content::WebContents*)webContents;
+
+// Given |webContents|, extracts a GURL to be used for Handoff. This may return
+// the empty GURL.
+- (GURL)handoffURLFromWebContents:(content::WebContents*)webContents;
 @end
 
 class AppControllerProfileObserver : public ProfileInfoCacheObserver {
@@ -776,6 +798,12 @@ class AppControllerProfileObserver : public ProfileInfoCacheObserver {
 
   startupComplete_ = YES;
 
+  Browser* browser =
+      FindLastActiveWithHostDesktopType(chrome::HOST_DESKTOP_TYPE_NATIVE);
+  content::WebContents* activeWebContents = nullptr;
+  if (browser)
+    activeWebContents = browser->tab_strip_model()->GetActiveWebContents();
+  [self updateHandoffManager:activeWebContents];
   [self openStartupUrls];
 
   PrefService* localState = g_browser_process->local_state();
@@ -786,6 +814,9 @@ class AppControllerProfileObserver : public ProfileInfoCacheObserver {
         base::Bind(&chrome::BrowserCommandController::UpdateOpenFileState,
                    menuState_.get()));
   }
+
+  handoff_active_url_observer_bridge_.reset(
+      new HandoffActiveURLObserverBridge(self));
 }
 
 // This is called after profiles have been loaded and preferences registered.
@@ -1638,6 +1669,53 @@ class AppControllerProfileObserver : public ProfileInfoCacheObserver {
                                     error:(NSError*)error {
 }
 
+#pragma mark - Handoff Manager
+
+- (BOOL)shouldUseHandoff {
+  return base::mac::IsOSYosemiteOrLater();
+}
+
+- (void)passURLToHandoffManager:(const GURL&)handoffURL {
+  [handoffManager_ updateActiveURL:handoffURL];
+}
+
+- (void)updateHandoffManager:(content::WebContents*)webContents {
+  if (![self shouldUseHandoff])
+    return;
+
+  if (!handoffManager_)
+    handoffManager_.reset([[HandoffManager alloc] init]);
+
+  GURL handoffURL = [self handoffURLFromWebContents:webContents];
+  [self passURLToHandoffManager:handoffURL];
+}
+
+- (GURL)handoffURLFromWebContents:(content::WebContents*)webContents {
+  if (!webContents)
+    return GURL();
+
+  Profile* profile =
+      Profile::FromBrowserContext(webContents->GetBrowserContext());
+  if (!profile)
+    return GURL();
+
+  // Handoff is not allowed from an incognito profile. To err on the safe side,
+  // also disallow Handoff from a guest profile.
+  if (profile->GetProfileType() != Profile::REGULAR_PROFILE)
+    return GURL();
+
+  if (!webContents)
+    return GURL();
+
+  return webContents->GetVisibleURL();
+}
+
+#pragma mark - HandoffActiveURLObserverBridgeDelegate
+
+- (void)handoffActiveURLChanged:(content::WebContents*)webContents {
+  [self updateHandoffManager:webContents];
+}
+
 @end  // @implementation AppController
 
 //---------------------------------------------------------------------------
diff --git a/chrome/browser/app_controller_mac_browsertest.mm b/chrome/browser/app_controller_mac_browsertest.mm
index a136a12..0400188 100644
--- a/chrome/browser/app_controller_mac_browsertest.mm
+++ b/chrome/browser/app_controller_mac_browsertest.mm
@@ -35,9 +35,11 @@
 #include "chrome/common/pref_names.h"
 #include "chrome/common/url_constants.h"
 #include "chrome/test/base/in_process_browser_test.h"
+#include "chrome/test/base/ui_test_utils.h"
 #include "components/bookmarks/test/bookmark_test_helpers.h"
 #include "components/signin/core/common/profile_management_switches.h"
 #include "content/public/browser/web_contents.h"
+#include "content/public/test/browser_test_utils.h"
 #include "content/public/test/test_navigation_observer.h"
 #include "extensions/browser/app_window/app_window_registry.h"
 #include "extensions/common/extension.h"
@@ -481,3 +483,144 @@ IN_PROC_BROWSER_TEST_F(AppControllerMainMenuBrowserTest,
 }
 
 }  // namespace
+
+//--------------------------AppControllerHandoffBrowserTest---------------------
+
+static GURL g_handoff_url;
+
+@interface AppController (BrowserTest)
+- (BOOL)new_shouldUseHandoff;
+- (void)new_passURLToHandoffManager:(const GURL&)handoffURL;
+@end
+
+@implementation AppController (BrowserTest)
+- (BOOL)new_shouldUseHandoff {
+  return YES;
+}
+
+- (void)new_passURLToHandoffManager:(const GURL&)handoffURL {
+  g_handoff_url = handoffURL;
+}
+@end
+
+namespace {
+
+class AppControllerHandoffBrowserTest : public InProcessBrowserTest {
+ protected:
+  AppControllerHandoffBrowserTest() {}
+
+  // Exchanges the implementations of the two selectors on the class
+  // AppController.
+  void ExchangeSelectors(SEL originalMethod, SEL newMethod) {
+    Class appControllerClass = NSClassFromString(@"AppController");
+
+    ASSERT_TRUE(appControllerClass != nil);
+
+    Method original =
+        class_getInstanceMethod(appControllerClass, originalMethod);
+    Method destination = class_getInstanceMethod(appControllerClass, newMethod);
+
+    ASSERT_TRUE(original != NULL);
+    ASSERT_TRUE(destination != NULL);
+
+    method_exchangeImplementations(original, destination);
+  }
+
+  // Swizzle Handoff related implementations.
+  void SetUpInProcessBrowserTestFixture() override {
+    // Handoff is only available on OSX 10.10+. This swizzle makes the logic
+    // run on all OSX versions.
+    SEL originalMethod = @selector(shouldUseHandoff);
+    SEL newMethod = @selector(new_shouldUseHandoff);
+    ExchangeSelectors(originalMethod, newMethod);
+
+    // This swizzle intercepts the URL that would be sent to the Handoff
+    // Manager, and instead puts it into a variable accessible to this test.
+    originalMethod = @selector(passURLToHandoffManager:);
+    newMethod = @selector(new_passURLToHandoffManager:);
+    ExchangeSelectors(originalMethod, newMethod);
+  }
+
+  // Closes the tab, and waits for the close to finish.
+  void CloseTab(Browser* browser, int index) {
+    content::WebContentsDestroyedWatcher destroyed_watcher(
+        browser->tab_strip_model()->GetWebContentsAt(index));
+    browser->tab_strip_model()->CloseWebContentsAt(
+        index, TabStripModel::CLOSE_CREATE_HISTORICAL_TAB);
+    destroyed_watcher.Wait();
+  }
+};
+
+// Tests that as a user switches between tabs, navigates within a tab, and
+// switches between browser windows, the correct URL is being passed to the
+// Handoff.
+IN_PROC_BROWSER_TEST_F(AppControllerHandoffBrowserTest, TestHandoffURLs) {
+  ASSERT_TRUE(embedded_test_server()->InitializeAndWaitUntilReady());
+  EXPECT_EQ(g_handoff_url, GURL(url::kAboutBlankURL));
+
+  // Test that navigating to a URL updates the handoff URL.
+  GURL test_url1 = embedded_test_server()->GetURL("/title1.html");
+  ui_test_utils::NavigateToURL(browser(), test_url1);
+  EXPECT_EQ(g_handoff_url, test_url1);
+
+  // Test that opening a new tab updates the handoff URL.
+  GURL test_url2 = embedded_test_server()->GetURL("/title2.html");
+  chrome::NavigateParams params(browser(), test_url2, ui::PAGE_TRANSITION_LINK);
+  params.disposition = NEW_FOREGROUND_TAB;
+  ui_test_utils::NavigateToURL(&params);
+  EXPECT_EQ(g_handoff_url, test_url2);
+
+  // Test that switching tabs updates the handoff URL.
+  browser()->tab_strip_model()->ActivateTabAt(0, true);
+  EXPECT_EQ(g_handoff_url, test_url1);
+
+  // Test that closing the current tab updates the handoff URL.
+  CloseTab(browser(), 0);
+  EXPECT_EQ(g_handoff_url, test_url2);
+
+  // Test that opening a new browser window updates the handoff URL.
+  GURL test_url3 = embedded_test_server()->GetURL("/title3.html");
+  ui_test_utils::NavigateToURLWithDisposition(
+      browser(), GURL(test_url3), NEW_WINDOW,
+      ui_test_utils::BROWSER_TEST_WAIT_FOR_BROWSER);
+  EXPECT_EQ(g_handoff_url, test_url3);
+
+  // Check that there are exactly 2 browsers.
+  BrowserList* active_browser_list =
+      BrowserList::GetInstance(chrome::GetActiveDesktop());
+  EXPECT_EQ(2u, active_browser_list->size());
+
+  // Close the one and only tab for the second browser window.
+  Browser* browser2 = active_browser_list->get(1);
+  CloseTab(browser2, 0);
+  base::RunLoop().RunUntilIdle();
+  EXPECT_EQ(g_handoff_url, test_url2);
+
+  // The URLs of incognito windows should not be passed to Handoff.
+  GURL test_url4 = embedded_test_server()->GetURL("/simple.html");
+  ui_test_utils::NavigateToURLWithDisposition(
+      browser(), GURL(test_url4), OFF_THE_RECORD,
+      ui_test_utils::BROWSER_TEST_WAIT_FOR_BROWSER);
+  EXPECT_EQ(g_handoff_url, GURL());
+
+  // Open a new tab in the incognito window.
+  EXPECT_EQ(2u, active_browser_list->size());
+  Browser* browser3 = active_browser_list->get(1);
+  ui_test_utils::NavigateToURLWithDisposition(
+      browser3, test_url4, NEW_FOREGROUND_TAB,
+      ui_test_utils::BROWSER_TEST_WAIT_FOR_TAB);
+  EXPECT_EQ(g_handoff_url, GURL());
+
+  // Navigate the current tab in the incognito window.
+  ui_test_utils::NavigateToURLWithDisposition(
+      browser3, test_url1, CURRENT_TAB,
+      ui_test_utils::BROWSER_TEST_WAIT_FOR_NAVIGATION);
+  EXPECT_EQ(g_handoff_url, GURL());
+
+  // Activate the original browser window.
+  Browser* browser1 = active_browser_list->get(0);
+  browser1->window()->Show();
+  EXPECT_EQ(g_handoff_url, test_url2);
+}
+
+}  // namespace
diff --git a/chrome/browser/ui/cocoa/handoff_active_url_observer.cc b/chrome/browser/ui/cocoa/handoff_active_url_observer.cc
new file mode 100644
index 0000000..592a757
--- /dev/null
+++ b/chrome/browser/ui/cocoa/handoff_active_url_observer.cc
@@ -0,0 +1,124 @@
+// 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.
+
+#include "chrome/browser/ui/cocoa/handoff_active_url_observer.h"
+
+#include "base/logging.h"
+#include "chrome/browser/ui/browser_finder.h"
+#include "chrome/browser/ui/browser_list.h"
+#include "chrome/browser/ui/cocoa/handoff_active_url_observer_delegate.h"
+#include "chrome/browser/ui/tabs/tab_strip_model.h"
+#include "content/public/browser/web_contents.h"
+
+HandoffActiveURLObserver::HandoffActiveURLObserver(
+    HandoffActiveURLObserverDelegate* delegate)
+    : delegate_(delegate),
+      active_tab_strip_model_(nullptr),
+      active_browser_(nullptr) {
+  DCHECK(delegate_);
+
+  active_browser_ = chrome::FindLastActiveWithHostDesktopType(
+      chrome::HOST_DESKTOP_TYPE_NATIVE);
+  BrowserList::AddObserver(this);
+  UpdateObservations();
+}
+
+HandoffActiveURLObserver::~HandoffActiveURLObserver() {
+  BrowserList::RemoveObserver(this);
+  StopObservingTabStripModel();
+  StopObservingWebContents();
+}
+
+void HandoffActiveURLObserver::OnBrowserSetLastActive(Browser* browser) {
+  active_browser_ = browser;
+  UpdateObservations();
+  delegate_->HandoffActiveURLChanged(GetActiveWebContents());
+}
+
+void HandoffActiveURLObserver::OnBrowserRemoved(Browser* removed_browser) {
+  if (active_browser_ != removed_browser)
+    return;
+
+  active_browser_ = chrome::FindLastActiveWithHostDesktopType(
+      chrome::HOST_DESKTOP_TYPE_NATIVE);
+  UpdateObservations();
+  delegate_->HandoffActiveURLChanged(GetActiveWebContents());
+}
+
+void HandoffActiveURLObserver::ActiveTabChanged(
+    content::WebContents* old_contents,
+    content::WebContents* new_contents,
+    int index,
+    int reason) {
+  StartObservingWebContents(new_contents);
+  delegate_->HandoffActiveURLChanged(new_contents);
+}
+
+void HandoffActiveURLObserver::TabStripModelDeleted() {
+  StopObservingTabStripModel();
+  StopObservingWebContents();
+}
+
+void HandoffActiveURLObserver::DidNavigateMainFrame(
+    const content::LoadCommittedDetails& details,
+    const content::FrameNavigateParams& params) {
+  delegate_->HandoffActiveURLChanged(web_contents());
+}
+
+void HandoffActiveURLObserver::WebContentsDestroyed() {
+  StopObservingWebContents();
+}
+
+void HandoffActiveURLObserver::UpdateObservations() {
+  if (!active_browser_) {
+    StopObservingTabStripModel();
+    StopObservingWebContents();
+    return;
+  }
+
+  TabStripModel* model = active_browser_->tab_strip_model();
+  StartObservingTabStripModel(model);
+
+  content::WebContents* web_contents = model->GetActiveWebContents();
+  if (web_contents)
+    StartObservingWebContents(web_contents);
+  else
+    StopObservingWebContents();
+}
+
+void HandoffActiveURLObserver::StartObservingTabStripModel(
+    TabStripModel* tab_strip_model) {
+  DCHECK(tab_strip_model);
+
+  if (active_tab_strip_model_ == tab_strip_model)
+    return;
+
+  StopObservingTabStripModel();
+  tab_strip_model->AddObserver(this);
+  active_tab_strip_model_ = tab_strip_model;
+}
+
+void HandoffActiveURLObserver::StopObservingTabStripModel() {
+  if (active_tab_strip_model_) {
+    active_tab_strip_model_->RemoveObserver(this);
+    active_tab_strip_model_ = nullptr;
+  }
+}
+
+void HandoffActiveURLObserver::StartObservingWebContents(
+    content::WebContents* web_contents) {
+  DCHECK(web_contents);
+  Observe(web_contents);
+}
+
+void HandoffActiveURLObserver::StopObservingWebContents() {
+  Observe(nullptr);
+}
+
+content::WebContents* HandoffActiveURLObserver::GetActiveWebContents() {
+  if (!active_browser_)
+    return nullptr;
+
+  return active_browser_->tab_strip_model()->GetActiveWebContents();
+}
diff --git a/chrome/browser/ui/cocoa/handoff_active_url_observer.h b/chrome/browser/ui/cocoa/handoff_active_url_observer.h
new file mode 100644
index 0000000..a46ed98
--- /dev/null
+++ b/chrome/browser/ui/cocoa/handoff_active_url_observer.h
@@ -0,0 +1,83 @@
+// 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_H_
+#define CHROME_BROWSER_UI_COCOA_HANDOFF_ACTIVE_URL_OBSERVER_H_
+
+#include "chrome/browser/ui/browser_list_observer.h"
+#include "chrome/browser/ui/tabs/tab_strip_model_observer.h"
+#include "content/public/browser/web_contents_observer.h"
+
+namespace content {
+class WebContents;
+}
+
+class Browser;
+class HandoffActiveURLObserverDelegate;
+class TabStripModel;
+
+// This class observes changes to the "active URL". This is defined as the
+// visible URL of the WebContents of the selected tab of the most recently
+// focused browser window.
+class HandoffActiveURLObserver : public chrome::BrowserListObserver,
+                                 public TabStripModelObserver,
+                                 public content::WebContentsObserver {
+ public:
+  explicit HandoffActiveURLObserver(HandoffActiveURLObserverDelegate* delegate);
+  ~HandoffActiveURLObserver() override;
+
+ private:
+  // chrome::BrowserListObserver
+  void OnBrowserSetLastActive(Browser* browser) override;
+  void OnBrowserRemoved(Browser* browser) override;
+
+  // TabStripModelObserver
+  void ActiveTabChanged(content::WebContents* old_contents,
+                        content::WebContents* new_contents,
+                        int index,
+                        int reason) override;
+  void TabStripModelDeleted() override;
+
+  // content::WebContentsObserver
+  void DidNavigateMainFrame(
+      const content::LoadCommittedDetails& details,
+      const content::FrameNavigateParams& params) override;
+  void WebContentsDestroyed() override;
+
+  // This method ensures that the instance is registered as an observer of the
+  // correct TabStripModel and WebContents for |active_browser_|.
+  void UpdateObservations();
+
+  // Makes this object start observing the TabStripModel, if it is not already
+  // doing so. This method is idempotent.
+  void StartObservingTabStripModel(TabStripModel* tab_strip_model);
+
+  // Makes this object stop observing the TabStripModel.
+  void StopObservingTabStripModel();
+
+  // Makes this object start observing the WebContents, if it is not already
+  // doing so. This method is idempotent.
+  void StartObservingWebContents(content::WebContents* web_contents);
+
+  // Makes this object stop observing the WebContents.
+  void StopObservingWebContents();
+
+  // Returns the active WebContents. May return nullptr.
+  content::WebContents* GetActiveWebContents();
+
+  // Instances of this class should be owned by their |delegate_|.
+  HandoffActiveURLObserverDelegate* delegate_;
+
+  // When this pointer is not nullptr, this object is registered as an observer
+  // of the TabStripModel.
+  TabStripModel* active_tab_strip_model_;
+
+  // This pointer is always up to date, and points to the most recently
+  // activated browser, or nullptr if no browsers exist.
+  Browser* active_browser_;
+
+  DISALLOW_COPY_AND_ASSIGN(HandoffActiveURLObserver);
+};
+
+#endif  // CHROME_BROWSER_UI_COCOA_HANDOFF_ACTIVE_URL_OBSERVER_H_
diff --git a/chrome/browser/ui/cocoa/handoff_active_url_observer_bridge.h b/chrome/browser/ui/cocoa/handoff_active_url_observer_bridge.h
new file mode 100644
index 0000000..0d00961
--- /dev/null
+++ b/chrome/browser/ui/cocoa/handoff_active_url_observer_bridge.h
@@ -0,0 +1,47 @@
+// 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_BRIDGE_H_
+#define CHROME_BROWSER_UI_COCOA_HANDOFF_ACTIVE_URL_OBSERVER_BRIDGE_H_
+
+#import <Cocoa/Cocoa.h>
+
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "chrome/browser/ui/cocoa/handoff_active_url_observer_delegate.h"
+
+namespace content {
+class WebContents;
+}
+
+class HandoffActiveURLObserver;
+
+// A protocol that allows ObjC objects to receive delegate callbacks from
+// HandoffActiveURLObserver.
+@protocol HandoffActiveURLObserverBridgeDelegate
+- (void)handoffActiveURLChanged:(content::WebContents*)webContents;
+@end
+
+// This class allows an ObjC object to receive the delegate callbacks from an
+// HandoffActiveURLObserver.
+class HandoffActiveURLObserverBridge : public HandoffActiveURLObserverDelegate {
+ public:
+  explicit HandoffActiveURLObserverBridge(
+      NSObject<HandoffActiveURLObserverBridgeDelegate>* delegate);
+
+  ~HandoffActiveURLObserverBridge() override;
+
+ private:
+  void HandoffActiveURLChanged(content::WebContents* web_contents) override;
+
+  // Instances of this class should be owned by their |delegate_|.
+  NSObject<HandoffActiveURLObserverBridgeDelegate>* delegate_;
+
+  // The C++ object that this class acts as a bridge for.
+  scoped_ptr<HandoffActiveURLObserver> observer_;
+
+  DISALLOW_COPY_AND_ASSIGN(HandoffActiveURLObserverBridge);
+};
+
+#endif  // CHROME_BROWSER_UI_COCOA_HANDOFF_ACTIVE_URL_OBSERVER_BRIDGE_H_
diff --git a/chrome/browser/ui/cocoa/handoff_active_url_observer_bridge.mm b/chrome/browser/ui/cocoa/handoff_active_url_observer_bridge.mm
new file mode 100644
index 0000000..639ae93
--- /dev/null
+++ b/chrome/browser/ui/cocoa/handoff_active_url_observer_bridge.mm
@@ -0,0 +1,21 @@
+// 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.
+
+#include "chrome/browser/ui/cocoa/handoff_active_url_observer_bridge.h"
+
+#include "chrome/browser/ui/cocoa/handoff_active_url_observer.h"
+
+HandoffActiveURLObserverBridge::HandoffActiveURLObserverBridge(
+    NSObject<HandoffActiveURLObserverBridgeDelegate>* delegate)
+    : delegate_(delegate) {
+  DCHECK(delegate_);
+  observer_.reset(new HandoffActiveURLObserver(this));
+}
+
+HandoffActiveURLObserverBridge::~HandoffActiveURLObserverBridge(){};
+
+void HandoffActiveURLObserverBridge::HandoffActiveURLChanged(
+    content::WebContents* web_contents) {
+  [delegate_ handoffActiveURLChanged:web_contents];
+}
diff --git a/chrome/browser/ui/cocoa/handoff_active_url_observer_delegate.h b/chrome/browser/ui/cocoa/handoff_active_url_observer_delegate.h
new file mode 100644
index 0000000..d0d0fff
--- /dev/null
+++ b/chrome/browser/ui/cocoa/handoff_active_url_observer_delegate.h
@@ -0,0 +1,27 @@
+// 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_