Implement BiDi support and replace ID support for notifications.

BUG=none
TEST=layout tests

Review URL: http://codereview.chromium.org/1917004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@52090 0039d316-1c4b-4281-b951-d872f2087c98

8 files changed, 186 insertions, 90 deletions

diff --git a/chrome/browser/notifications/balloon.cc b/chrome/browser/notifications/balloon.cc
index 4d9a94f..969bde1 100644
--- a/chrome/browser/notifications/balloon.cc
+++ b/chrome/browser/notifications/balloon.cc
@@ -38,10 +38,12 @@ void Balloon::Show() {
   notification_->Display();
   if (balloon_view_.get()) {
     balloon_view_->Show(this);
+    balloon_view_->RepositionToBalloon();
   }
 }
 
 void Balloon::Update(const Notification& notification) {
+  notification_->Close(false);
   notification_.reset(new Notification(notification));
   notification_->Display();
   if (balloon_view_.get()) {
diff --git a/chrome/browser/notifications/desktop_notification_service.cc b/chrome/browser/notifications/desktop_notification_service.cc
index 4a5f3ab..bc66077 100644
--- a/chrome/browser/notifications/desktop_notification_service.cc
+++ b/chrome/browser/notifications/desktop_notification_service.cc
@@ -36,12 +36,14 @@
 #include "third_party/WebKit/WebKit/chromium/public/WebNotificationPresenter.h"
 
 using WebKit::WebNotificationPresenter;
+using WebKit::WebTextDirection;
 
 const ContentSetting kDefaultSetting = CONTENT_SETTING_ASK;
 
 // static
 string16 DesktopNotificationService::CreateDataUrl(
-    const GURL& icon_url, const string16& title, const string16& body) {
+    const GURL& icon_url, const string16& title, const string16& body,
+    WebTextDirection dir) {
   int resource;
   string16 line_name;
   string16 line;
@@ -51,6 +53,9 @@ string16 DesktopNotificationService::CreateDataUrl(
     subst.push_back(icon_url.spec());
     subst.push_back(EscapeForHTML(UTF16ToUTF8(title)));
     subst.push_back(EscapeForHTML(UTF16ToUTF8(body)));
+    // icon float position
+    subst.push_back(dir == WebKit::WebTextDirectionRightToLeft ?
+                    "right" : "left");
   } else if (title.empty() || body.empty()) {
     resource = IDR_NOTIFICATION_1LINE_HTML;
     line = title.empty() ? body : title;
@@ -64,6 +69,9 @@ string16 DesktopNotificationService::CreateDataUrl(
     subst.push_back(EscapeForHTML(UTF16ToUTF8(title)));
     subst.push_back(EscapeForHTML(UTF16ToUTF8(body)));
   }
+  // body text direction
+  subst.push_back(dir == WebKit::WebTextDirectionRightToLeft ?
+                  "rtl" : "ltr");
 
   const base::StringPiece template_html(
       ResourceBundle::GetSharedInstance().GetRawDataResource(
@@ -529,37 +537,32 @@ bool DesktopNotificationService::CancelDesktopNotification(
   scoped_refptr<NotificationObjectProxy> proxy(
       new NotificationObjectProxy(process_id, route_id, notification_id,
                                   false));
-  Notification notif(GURL(), GURL(), L"", proxy);
+  // TODO(johnnyg): clean up this "empty" notification.
+  Notification notif(GURL(), GURL(), L"", ASCIIToUTF16(""), proxy);
   return ui_manager_->Cancel(notif);
 }
 
 
 bool DesktopNotificationService::ShowDesktopNotification(
-    const GURL& origin, const GURL& url, int process_id, int route_id,
-    DesktopNotificationSource source, int notification_id) {
+    const ViewHostMsg_ShowNotification_Params& params,
+    int process_id, int route_id, DesktopNotificationSource source) {
   DCHECK(ChromeThread::CurrentlyOn(ChromeThread::UI));
+  const GURL& origin = params.origin;
   NotificationObjectProxy* proxy =
       new NotificationObjectProxy(process_id, route_id,
-                                  notification_id,
+                                  params.notification_id,
                                   source == WorkerNotification);
-  Notification notif(origin, url, DisplayNameForOrigin(origin), proxy);
-  ShowNotification(notif);
-  return true;
-}
-
-bool DesktopNotificationService::ShowDesktopNotificationText(
-    const GURL& origin, const GURL& icon, const string16& title,
-    const string16& text, int process_id, int route_id,
-    DesktopNotificationSource source, int notification_id) {
-  DCHECK(ChromeThread::CurrentlyOn(ChromeThread::UI));
-  NotificationObjectProxy* proxy =
-      new NotificationObjectProxy(process_id, route_id,
-                                  notification_id,
-                                  source == WorkerNotification);
-  // "upconvert" the string parameters to a data: URL.
-  string16 data_url = CreateDataUrl(icon, title, text);
+  GURL contents;
+  if (params.is_html) {
+    contents = params.contents_url;
+  } else {
+    // "upconvert" the string parameters to a data: URL.
+    contents = GURL(
+        CreateDataUrl(params.icon_url, params.title, params.body,
+                      params.direction));
+  }
   Notification notif(
-      origin, GURL(data_url), DisplayNameForOrigin(origin), proxy);
+      origin, contents, DisplayNameForOrigin(origin), params.replace_id, proxy);
   ShowNotification(notif);
   return true;
 }
diff --git a/chrome/browser/notifications/desktop_notification_service.h b/chrome/browser/notifications/desktop_notification_service.h
index 3f97425..ae38b18 100644
--- a/chrome/browser/notifications/desktop_notification_service.h
+++ b/chrome/browser/notifications/desktop_notification_service.h
@@ -14,6 +14,7 @@
 #include "chrome/common/notification_registrar.h"
 #include "chrome/common/notification_service.h"
 #include "googleurl/src/gurl.h"
+#include "third_party/WebKit/WebKit/chromium/public/WebTextDirection.h"
 
 class NotificationUIManager;
 class NotificationsPrefsCache;
@@ -21,6 +22,7 @@ class PrefService;
 class Profile;
 class Task;
 class TabContents;
+struct ViewHostMsg_ShowNotification_Params;
 
 // The DesktopNotificationService is an object, owned by the Profile,
 // which provides the creation of desktop "toasts" to web pages and workers.
@@ -44,23 +46,13 @@ class DesktopNotificationService : public NotificationObserver {
                          int callback_context,
                          TabContents* tab);
 
-  // Takes a notification object and shows it in the UI.
-  void ShowNotification(const Notification& notification);
-
-  // Two ShowNotification methods: getting content either from remote
-  // URL or as local parameters.  These are called on the UI thread
-  // in response to IPCs from a child process running script. |origin|
-  // is the origin of the script.  |source| indicates whether the
-  // script is in a worker or page.  |notification_id| is an opaque
-  // value to be passed back to the process when events occur on
-  // this notification.
-  bool ShowDesktopNotification(const GURL& origin, const GURL& url,
-      int process_id, int route_id, DesktopNotificationSource source,
-      int notification_id);
-  bool ShowDesktopNotificationText(const GURL& origin, const GURL& icon,
-      const string16& title, const string16& text, int process_id,
-      int route_id, DesktopNotificationSource source, int notification_id);
-
+  // ShowNotification is called on the UI thread handling IPCs from a child
+  // process, identified by |process_id| and |route_id|.  |source| indicates
+  // whether the script is in a worker or page. |params| contains all the
+  // other parameters supplied by the worker or page.
+  bool ShowDesktopNotification(
+      const ViewHostMsg_ShowNotification_Params& params,
+      int process_id, int route_id, DesktopNotificationSource source);
 
   // Cancels a notification.  If it has already been shown, it will be
   // removed from the screen.  If it hasn't been shown yet, it won't be
@@ -83,8 +75,10 @@ class DesktopNotificationService : public NotificationObserver {
   // Creates a data:xxxx URL which contains the full HTML for a notification
   // using supplied icon, title, and text, run through a template which contains
   // the standard formatting for notifications.
-  static string16 CreateDataUrl(const GURL& icon_url, const string16& title,
-                                const string16& body);
+  static string16 CreateDataUrl(const GURL& icon_url,
+                                const string16& title,
+                                const string16& body,
+                                WebKit::WebTextDirection dir);
 
   // The default content setting determines how to handle origins that haven't
   // been allowed or denied yet.
@@ -112,6 +106,9 @@ class DesktopNotificationService : public NotificationObserver {
   void StartObserving();
   void StopObserving();
 
+  // Takes a notification object and shows it in the UI.
+  void ShowNotification(const Notification& notification);
+
   // Save a permission change to the profile.
   void PersistPermissionChange(const GURL& origin, bool is_allowed);
 
diff --git a/chrome/browser/notifications/desktop_notifications_unittest.cc b/chrome/browser/notifications/desktop_notifications_unittest.cc
index 5cd03c3..459d9a0 100644
--- a/chrome/browser/notifications/desktop_notifications_unittest.cc
+++ b/chrome/browser/notifications/desktop_notifications_unittest.cc
@@ -21,6 +21,7 @@ void MockBalloonCollection::Add(const Notification& notification,
   Notification test_notification(notification.origin_url(),
                                  notification.content_url(),
                                  notification.display_source(),
+                                 string16(), /* replace_id */
                                  log_proxy_.get());
   BalloonCollectionImpl::Add(test_notification, profile);
 }
@@ -29,6 +30,7 @@ bool MockBalloonCollection::Remove(const Notification& notification) {
   Notification test_notification(notification.origin_url(),
                                  notification.content_url(),
                                  notification.display_source(),
+                                 string16(), /* replace_id */
                                  log_proxy_.get());
   return BalloonCollectionImpl::Remove(test_notification);
 }
@@ -87,18 +89,35 @@ void DesktopNotificationsTest::TearDown() {
   ui_manager_.reset(NULL);
 }
 
+ViewHostMsg_ShowNotification_Params
+DesktopNotificationsTest::StandardTestNotification() {
+  ViewHostMsg_ShowNotification_Params params;
+  params.notification_id = 0;
+  params.origin = GURL("http://www.google.com");
+  params.is_html = false;
+  params.icon_url = GURL("/icon.png");
+  params.title = ASCIIToUTF16("Title");
+  params.body = ASCIIToUTF16("Text");
+  return params;
+}
+
 TEST_F(DesktopNotificationsTest, TestShow) {
-  EXPECT_TRUE(service_->ShowDesktopNotificationText(
-      GURL("http://www.google.com"),
-      GURL("/icon.png"), ASCIIToUTF16("Title"), ASCIIToUTF16("Text"),
-      0, 0, DesktopNotificationService::PageNotification, 1));
+  ViewHostMsg_ShowNotification_Params params = StandardTestNotification();
+  params.notification_id = 1;
+
+  EXPECT_TRUE(service_->ShowDesktopNotification(
+      params, 0, 0, DesktopNotificationService::PageNotification));
   MessageLoopForUI::current()->RunAllPending();
   EXPECT_EQ(1, balloon_collection_->count());
 
+  ViewHostMsg_ShowNotification_Params params2;
+  params2.origin = GURL("http://www.google.com");
+  params2.is_html = true;
+  params2.contents_url = GURL("http://www.google.com/notification.html");
+  params2.notification_id = 2;
+
   EXPECT_TRUE(service_->ShowDesktopNotification(
-      GURL("http://www.google.com"),
-      GURL("http://www.google.com/notification.html"),
-      0, 0, DesktopNotificationService::PageNotification, 2));
+      params2, 0, 0, DesktopNotificationService::PageNotification));
   MessageLoopForUI::current()->RunAllPending();
   EXPECT_EQ(2, balloon_collection_->count());
 
@@ -108,11 +127,12 @@ TEST_F(DesktopNotificationsTest, TestShow) {
 }
 
 TEST_F(DesktopNotificationsTest, TestClose) {
+  ViewHostMsg_ShowNotification_Params params = StandardTestNotification();
+  params.notification_id = 1;
+
   // Request a notification; should open a balloon.
-  EXPECT_TRUE(service_->ShowDesktopNotificationText(
-      GURL("http://www.google.com"),
-      GURL("/icon.png"), ASCIIToUTF16("Title"), ASCIIToUTF16("Text"),
-      0, 0, DesktopNotificationService::PageNotification, 1));
+  EXPECT_TRUE(service_->ShowDesktopNotification(
+      params, 0, 0, DesktopNotificationService::PageNotification));
   MessageLoopForUI::current()->RunAllPending();
   EXPECT_EQ(1, balloon_collection_->count());
 
@@ -130,12 +150,14 @@ TEST_F(DesktopNotificationsTest, TestCancel) {
   int process_id = 0;
   int route_id = 0;
   int notification_id = 1;
+
+  ViewHostMsg_ShowNotification_Params params = StandardTestNotification();
+  params.notification_id = notification_id;
+
   // Request a notification; should open a balloon.
-  EXPECT_TRUE(service_->ShowDesktopNotificationText(
-      GURL("http://www.google.com"),
-      GURL("/icon.png"), ASCIIToUTF16("Title"), ASCIIToUTF16("Text"),
-      process_id, route_id, DesktopNotificationService::PageNotification,
-      notification_id));
+  EXPECT_TRUE(service_->ShowDesktopNotification(
+      params, process_id, route_id,
+      DesktopNotificationService::PageNotification));
   MessageLoopForUI::current()->RunAllPending();
   EXPECT_EQ(1, balloon_collection_->count());
 
@@ -154,15 +176,15 @@ TEST_F(DesktopNotificationsTest, TestCancel) {
 
 #if defined(OS_WIN) || defined(TOOLKIT_VIEWS)
 TEST_F(DesktopNotificationsTest, TestPositioning) {
+  ViewHostMsg_ShowNotification_Params params = StandardTestNotification();
   std::string expected_log;
   // Create some toasts.  After each but the first, make sure there
   // is a minimum separation between the toasts.
   int last_top = 0;
   for (int id = 0; id <= 3; ++id) {
-    EXPECT_TRUE(service_->ShowDesktopNotificationText(
-        GURL("http://www.google.com"),
-        GURL("/icon.png"), ASCIIToUTF16("Title"), ASCIIToUTF16("Text"),
-        0, 0, DesktopNotificationService::PageNotification, id));
+    params.notification_id = id;
+    EXPECT_TRUE(service_->ShowDesktopNotification(
+        params, 0, 0, DesktopNotificationService::PageNotification));
     expected_log.append("notification displayed\n");
     int top = balloon_collection_->UppermostVerticalPosition();
     if (id > 0)
@@ -174,21 +196,29 @@ TEST_F(DesktopNotificationsTest, TestPositioning) {
 }
 
 TEST_F(DesktopNotificationsTest, TestVariableSize) {
+  ViewHostMsg_ShowNotification_Params params;
+  params.origin = GURL("http://long.google.com");
+  params.is_html = false;
+  params.icon_url = GURL("/icon.png");
+  params.title = ASCIIToUTF16("Really Really Really Really Really Really "
+                              "Really Really Really Really Really Really "
+                              "Really Really Really Really Really Really "
+                              "Really Long Title"),
+  params.body = ASCIIToUTF16("Text");
+  params.notification_id = 0;
+
   std::string expected_log;
   // Create some toasts.  After each but the first, make sure there
   // is a minimum separation between the toasts.
-  EXPECT_TRUE(service_->ShowDesktopNotificationText(
-      GURL("http://long.google.com"), GURL("/icon.png"),
-      ASCIIToUTF16("Really Really Really Really Really Really "
-          "Really Really Really Really Really Really "
-          "Really Really Really Really Really Really Really Long Title"),
-      ASCIIToUTF16("Text"),
-      0, 0, DesktopNotificationService::PageNotification, 0));
+  EXPECT_TRUE(service_->ShowDesktopNotification(
+      params, 0, 0, DesktopNotificationService::PageNotification));
   expected_log.append("notification displayed\n");
-  EXPECT_TRUE(service_->ShowDesktopNotificationText(
-      GURL("http://short.google.com"), GURL("/icon.png"),
-      ASCIIToUTF16("Short title"), ASCIIToUTF16("Text"),
-      0, 0, DesktopNotificationService::PageNotification, 1));
+
+  params.origin = GURL("http://short.google.com");
+  params.title = ASCIIToUTF16("Short title");
+  params.notification_id = 1;
+  EXPECT_TRUE(service_->ShowDesktopNotification(
+      params, 0, 0, DesktopNotificationService::PageNotification));
   expected_log.append("notification displayed\n");
 
   std::deque<Balloon*>& balloons = balloon_collection_->balloons();
@@ -213,13 +243,13 @@ TEST_F(DesktopNotificationsTest, TestQueueing) {
   int route_id = 0;
 
   // Request lots of identical notifications.
+  ViewHostMsg_ShowNotification_Params params = StandardTestNotification();
   const int kLotsOfToasts = 20;
   for (int id = 1; id <= kLotsOfToasts; ++id) {
-    EXPECT_TRUE(service_->ShowDesktopNotificationText(
-        GURL("http://www.google.com"),
-        GURL("/icon.png"), ASCIIToUTF16("Title"), ASCIIToUTF16("Text"),
-        process_id, route_id,
-        DesktopNotificationService::PageNotification, id));
+    params.notification_id = id;
+    EXPECT_TRUE(service_->ShowDesktopNotification(
+        params, process_id, route_id,
+        DesktopNotificationService::PageNotification));
   }
   MessageLoopForUI::current()->RunAllPending();
 
@@ -265,11 +295,11 @@ TEST_F(DesktopNotificationsTest, TestQueueing) {
 TEST_F(DesktopNotificationsTest, TestEarlyDestruction) {
   // Create some toasts and then prematurely delete the notification service,
   // just to make sure nothing crashes/leaks.
+  ViewHostMsg_ShowNotification_Params params = StandardTestNotification();
   for (int id = 0; id <= 3; ++id) {
-    EXPECT_TRUE(service_->ShowDesktopNotificationText(
-        GURL("http://www.google.com"),
-        GURL("/icon.png"), ASCIIToUTF16("Title"), ASCIIToUTF16("Text"),
-        0, 0, DesktopNotificationService::PageNotification, id));
+    params.notification_id = id;
+    EXPECT_TRUE(service_->ShowDesktopNotification(
+        params, 0, 0, DesktopNotificationService::PageNotification));
   }
   service_.reset(NULL);
 }
@@ -277,12 +307,12 @@ TEST_F(DesktopNotificationsTest, TestEarlyDestruction) {
 TEST_F(DesktopNotificationsTest, TestUserInputEscaping) {
   // Create a test script with some HTML; assert that it doesn't get into the
   // data:// URL that's produced for the balloon.
-  EXPECT_TRUE(service_->ShowDesktopNotificationText(
-      GURL("http://www.google.com"),
-      GURL("/icon.png"),
-      ASCIIToUTF16("<script>window.alert('uh oh');</script>"),
-      ASCIIToUTF16("<i>this text is in italics</i>, as is %3ci%3ethis%3c/i%3e"),
-      0, 0, DesktopNotificationService::PageNotification, 1));
+  ViewHostMsg_ShowNotification_Params params = StandardTestNotification();
+  params.title = ASCIIToUTF16("<script>window.alert('uh oh');</script>");
+  params.body = ASCIIToUTF16("<i>this text is in italics</i>");
+  params.notification_id = 1;
+  EXPECT_TRUE(service_->ShowDesktopNotification(
+      params, 0, 0, DesktopNotificationService::PageNotification));
 
   MessageLoopForUI::current()->RunAllPending();
   EXPECT_EQ(1, balloon_collection_->count());
diff --git a/chrome/browser/notifications/desktop_notifications_unittest.h b/chrome/browser/notifications/desktop_notifications_unittest.h
index 46bfeb4e..56a2a6b 100644
--- a/chrome/browser/notifications/desktop_notifications_unittest.h
+++ b/chrome/browser/notifications/desktop_notifications_unittest.h
@@ -15,6 +15,7 @@
 #include "chrome/browser/notifications/notification_test_util.h"
 #include "chrome/browser/notifications/notification_ui_manager.h"
 #include "chrome/browser/notifications/notifications_prefs_cache.h"
+#include "chrome/common/render_messages.h"
 #include "chrome/test/testing_profile.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ -91,6 +92,9 @@ class DesktopNotificationsTest : public testing::Test {
     return service_->prefs_cache()->HasPermission(origin);
   }
 
+  // Constructs a notification parameter structure for use in tests.
+  ViewHostMsg_ShowNotification_Params StandardTestNotification();
+
   // Create a message loop to allow notifications code to post tasks,
   // and a thread so that notifications code runs on the expected thread.
   MessageLoopForUI message_loop_;
diff --git a/chrome/browser/notifications/notification.h b/chrome/browser/notifications/notification.h
index a58c2ad..bdad291 100644
--- a/chrome/browser/notifications/notification.h
+++ b/chrome/browser/notifications/notification.h
@@ -16,12 +16,15 @@ class NotificationDelegate;
 // data: URLs representing simple text+icon notifications.
 class Notification {
  public:
+  // TODO: http://crbug.com/43899 Convert this class to string16.
   Notification(const GURL& origin_url, const GURL& content_url,
                const std::wstring& display_source,
+               const string16& replace_id,
                NotificationDelegate* delegate)
       : origin_url_(origin_url),
         content_url_(content_url),
         display_source_(display_source),
+        replace_id_(replace_id),
         delegate_(delegate) {
   }
 
@@ -29,9 +32,18 @@ class Notification {
       : origin_url_(notification.origin_url()),
         content_url_(notification.content_url()),
         display_source_(notification.display_source()),
+        replace_id_(notification.replace_id()),
         delegate_(notification.delegate()) {
   }
 
+  void operator=(const Notification& notification) {
+    origin_url_ = notification.origin_url();
+    content_url_ = notification.content_url();
+    display_source_ = notification.display_source();
+    replace_id_ = notification.replace_id();
+    delegate_ = notification.delegate();
+  }
+
   // The URL (may be data:) containing the contents for the notification.
   const GURL& content_url() const { return content_url_; }
 
@@ -41,6 +53,8 @@ class Notification {
   // A display string for the source of the notification.
   const std::wstring& display_source() const { return display_source_; }
 
+  const string16& replace_id() const { return replace_id_; }
+
   void Display() const { delegate()->Display(); }
   void Error() const { delegate()->Error(); }
   void Close(bool by_user) const { delegate()->Close(by_user); }
@@ -63,12 +77,12 @@ class Notification {
   // the same as origin_url_, or the name of an extension.
   std::wstring display_source_;
 
+  // The replace ID for the notification.
+  string16 replace_id_;
+
   // A proxy object that allows access back to the JavaScript object that
   // represents the notification, for firing events.
   scoped_refptr<NotificationDelegate> delegate_;
-
-  // Disallow assign.  Copy constructor written above.
-  void operator=(const Notification&);
 };
 
 #endif  // CHROME_BROWSER_NOTIFICATIONS_NOTIFICATION_H_
diff --git a/chrome/browser/notifications/notification_ui_manager.cc b/chrome/browser/notifications/notification_ui_manager.cc
index e5ae3bd..42b9c5e 100644
--- a/chrome/browser/notifications/notification_ui_manager.cc
+++ b/chrome/browser/notifications/notification_ui_manager.cc
@@ -22,6 +22,10 @@ class QueuedNotification {
   const Notification& notification() const { return notification_; }
   Profile* profile() const { return profile_; }
 
+  void Replace(const Notification& new_notification) {
+    notification_ = new_notification;
+  }
+
  private:
   // The notification to be shown.
   Notification notification_;
@@ -51,6 +55,10 @@ NotificationUIManager* NotificationUIManager::Create() {
 
 void NotificationUIManager::Add(const Notification& notification,
                                 Profile* profile) {
+  if (TryReplacement(notification)) {
+    return;
+  }
+
   LOG(INFO) << "Added notification. URL: "
             << notification.content_url().spec().c_str();
   show_queue_.push_back(
@@ -88,3 +96,37 @@ void NotificationUIManager::ShowNotifications() {
 void NotificationUIManager::OnBalloonSpaceChanged() {
   CheckAndShowNotifications();
 }
+
+bool NotificationUIManager::TryReplacement(const Notification& notification) {
+  const GURL& origin = notification.origin_url();
+  const string16& replace_id = notification.replace_id();
+
+  if (replace_id.empty())
+    return false;
+
+  // First check the queue of pending notifications for replacement.
+  // Then check the list of notifications already being shown.
+  NotificationDeque::iterator iter;
+  for (iter = show_queue_.begin(); iter != show_queue_.end(); ++iter) {
+    if (origin == (*iter)->notification().origin_url() &&
+        replace_id == (*iter)->notification().replace_id()) {
+      (*iter)->Replace(notification);
+      return true;
+    }
+  }
+
+  BalloonCollection::Balloons::iterator balloon_iter;
+  BalloonCollection::Balloons balloons =
+      balloon_collection_->GetActiveBalloons();
+  for (balloon_iter = balloons.begin();
+       balloon_iter != balloons.end();
+       ++balloon_iter) {
+    if (origin == (*balloon_iter)->notification().origin_url() &&
+        replace_id == (*balloon_iter)->notification().replace_id()) {
+      (*balloon_iter)->Update(notification);
+      return true;
+    }
+  }
+
+  return false;
+}
diff --git a/chrome/browser/notifications/notification_ui_manager.h b/chrome/browser/notifications/notification_ui_manager.h
index 2eaedd3..e510e7f 100644
--- a/chrome/browser/notifications/notification_ui_manager.h
+++ b/chrome/browser/notifications/notification_ui_manager.h
@@ -61,6 +61,10 @@ class NotificationUIManager
   // BalloonCollectionObserver implementation.
   virtual void OnBalloonSpaceChanged();
 
+  // Replace an existing notification with this one if applicable;
+  // returns true if the replacement happened.
+  bool TryReplacement(const Notification& notification);
+
   // An owned pointer to the collection of active balloons.
   scoped_ptr<BalloonCollection> balloon_collection_;