Fix the problem that notifications and panels overlap.

The workaround is to move all notifications on top of the panels that could overlap with.

BUG=103052
TEST=new test


Review URL: http://codereview.chromium.org/8503037

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@109588 0039d316-1c4b-4281-b951-d872f2087c98

12 files changed, 408 insertions, 25 deletions

diff --git a/chrome/browser/notifications/balloon_collection_gtk.cc b/chrome/browser/notifications/balloon_collection_gtk.cc
index 2420735..5b8a784 100644
--- a/chrome/browser/notifications/balloon_collection_gtk.cc
+++ b/chrome/browser/notifications/balloon_collection_gtk.cc
@@ -35,6 +35,14 @@ int BalloonCollectionImpl::Layout::VerticalEdgeMargin() const {
   return 5;
 }
 
+bool BalloonCollectionImpl::Layout::NeedToMoveAboveLeftSidePanels() const {
+  return placement_ == VERTICALLY_FROM_BOTTOM_LEFT;
+}
+
+bool BalloonCollectionImpl::Layout::NeedToMoveAboveRightSidePanels() const {
+  return placement_ == VERTICALLY_FROM_BOTTOM_RIGHT;
+}
+
 void BalloonCollectionImpl::PositionBalloons(bool reposition) {
   PositionBalloonsInternal(reposition);
 }
@@ -92,6 +100,7 @@ void BalloonCollectionImpl::SetPositionPreference(
   else
     NOTREACHED();
 
+  layout_.ComputeOffsetToMoveAbovePanels(gfx::Rect());
   PositionBalloons(true);
 }
 
diff --git a/chrome/browser/notifications/balloon_collection_impl.cc b/chrome/browser/notifications/balloon_collection_impl.cc
index 9d234c2..173c78c 100644
--- a/chrome/browser/notifications/balloon_collection_impl.cc
+++ b/chrome/browser/notifications/balloon_collection_impl.cc
@@ -10,7 +10,13 @@
 #include "chrome/browser/notifications/balloon.h"
 #include "chrome/browser/notifications/balloon_host.h"
 #include "chrome/browser/notifications/notification.h"
+#include "chrome/browser/ui/browser.h"
+#include "chrome/browser/ui/panels/panel_manager.h"
+#include "chrome/browser/ui/panels/panel.h"
 #include "chrome/browser/ui/window_sizer.h"
+#include "chrome/common/chrome_notification_types.h"
+#include "content/public/browser/notification_registrar.h"
+#include "content/public/browser/notification_service.h"
 #include "ui/gfx/rect.h"
 #include "ui/gfx/size.h"
 
@@ -27,6 +33,9 @@ const int kMinAllowedBalloonCount = 2;
 // there is a relayout, in milliseconds.
 const int kRepositionDelay = 300;
 
+// The spacing between the balloon and the panel.
+const int kVerticalSpacingBetweenBalloonAndPanel = 5;
+
 }  // namespace
 
 BalloonCollectionImpl::BalloonCollectionImpl()
@@ -35,6 +44,12 @@ BalloonCollectionImpl::BalloonCollectionImpl()
       added_as_message_loop_observer_(false)
 #endif
 {
+  registrar_.Add(this, chrome::NOTIFICATION_PANEL_ADDED,
+                 content::NotificationService::AllSources());
+  registrar_.Add(this, chrome::NOTIFICATION_PANEL_REMOVED,
+                 content::NotificationService::AllSources());
+  registrar_.Add(this, chrome::NOTIFICATION_PANEL_CHANGED_BOUNDS,
+                 content::NotificationService::AllSources());
 
   SetPositionPreference(BalloonCollection::DEFAULT_POSITION);
 }
@@ -153,6 +168,26 @@ const BalloonCollection::Balloons& BalloonCollectionImpl::GetActiveBalloons() {
   return base_.balloons();
 }
 
+void BalloonCollectionImpl::Observe(
+    int type,
+    const content::NotificationSource& source,
+    const content::NotificationDetails& details) {
+  gfx::Rect bounds;
+  switch (type) {
+    case chrome::NOTIFICATION_PANEL_CHANGED_BOUNDS:
+      bounds = content::Source<Panel>(source).ptr()->GetBounds();
+      // Fall through.
+    case chrome::NOTIFICATION_PANEL_ADDED:
+    case chrome::NOTIFICATION_PANEL_REMOVED:
+      if (layout_.ComputeOffsetToMoveAbovePanels(bounds))
+        PositionBalloons(true);
+      break;
+    default:
+      NOTREACHED();
+      break;
+  }
+}
+
 void BalloonCollectionImpl::PositionBalloonsInternal(bool reposition) {
   const Balloons& balloons = base_.balloons();
 
@@ -231,7 +266,9 @@ void BalloonCollectionImpl::HandleMouseMoveEvent() {
 }
 #endif
 
-BalloonCollectionImpl::Layout::Layout() : placement_(INVALID) {
+BalloonCollectionImpl::Layout::Layout()
+    : placement_(INVALID),
+      offset_to_move_above_panels_(0) {
   RefreshSystemMetrics();
 }
 
@@ -245,24 +282,30 @@ void BalloonCollectionImpl::Layout::GetMaxLinearSize(int* max_balloon_size,
 }
 
 gfx::Point BalloonCollectionImpl::Layout::GetLayoutOrigin() const {
+  // For lower-left and lower-right positioning, we need to add an offset
+  // to ensure balloons to stay on top of panels to avoid overlapping.
   int x = 0;
   int y = 0;
   switch (placement_) {
-    case VERTICALLY_FROM_TOP_LEFT:
+    case VERTICALLY_FROM_TOP_LEFT: {
       x = work_area_.x() + HorizontalEdgeMargin();
-      y = work_area_.y() + VerticalEdgeMargin();
+      y = work_area_.y() + VerticalEdgeMargin() + offset_to_move_above_panels_;
       break;
-    case VERTICALLY_FROM_TOP_RIGHT:
+    }
+    case VERTICALLY_FROM_TOP_RIGHT: {
       x = work_area_.right() - HorizontalEdgeMargin();
-      y = work_area_.y() + VerticalEdgeMargin();
+      y = work_area_.y() + VerticalEdgeMargin() + offset_to_move_above_panels_;
       break;
+    }
     case VERTICALLY_FROM_BOTTOM_LEFT:
       x = work_area_.x() + HorizontalEdgeMargin();
-      y = work_area_.bottom() - VerticalEdgeMargin();
+      y = work_area_.bottom() - VerticalEdgeMargin() -
+          offset_to_move_above_panels_;
       break;
     case VERTICALLY_FROM_BOTTOM_RIGHT:
       x = work_area_.right() - HorizontalEdgeMargin();
-      y = work_area_.bottom() - VerticalEdgeMargin();
+      y = work_area_.bottom() - VerticalEdgeMargin() -
+          offset_to_move_above_panels_;
       break;
     default:
       NOTREACHED();
@@ -311,30 +354,21 @@ gfx::Point BalloonCollectionImpl::Layout::NextPosition(
 }
 
 gfx::Point BalloonCollectionImpl::Layout::OffScreenLocation() const {
-  int x = 0;
-  int y = 0;
+  gfx::Point location = GetLayoutOrigin();
   switch (placement_) {
     case VERTICALLY_FROM_TOP_LEFT:
-      x = work_area_.x() + HorizontalEdgeMargin();
-      y = work_area_.y() + kBalloonMaxHeight + VerticalEdgeMargin();
-      break;
-    case VERTICALLY_FROM_TOP_RIGHT:
-      x = work_area_.right() - kBalloonMaxWidth - HorizontalEdgeMargin();
-      y = work_area_.y() + kBalloonMaxHeight + VerticalEdgeMargin();
-      break;
     case VERTICALLY_FROM_BOTTOM_LEFT:
-      x = work_area_.x() + HorizontalEdgeMargin();
-      y = work_area_.bottom() + kBalloonMaxHeight + VerticalEdgeMargin();
+      location.Offset(0, kBalloonMaxHeight);
       break;
+    case VERTICALLY_FROM_TOP_RIGHT:
     case VERTICALLY_FROM_BOTTOM_RIGHT:
-      x = work_area_.right() - kBalloonMaxWidth - HorizontalEdgeMargin();
-      y = work_area_.bottom() + kBalloonMaxHeight + VerticalEdgeMargin();
+      location.Offset(-kBalloonMaxWidth, kBalloonMaxHeight);
       break;
     default:
       NOTREACHED();
       break;
   }
-  return gfx::Point(x, y);
+  return location;
 }
 
 bool BalloonCollectionImpl::Layout::RequiresOffsets() const {
@@ -363,6 +397,68 @@ gfx::Size BalloonCollectionImpl::Layout::ConstrainToSizeLimits(
                std::min(max_balloon_height(), size.height())));
 }
 
+bool BalloonCollectionImpl::Layout::ComputeOffsetToMoveAbovePanels(
+    const gfx::Rect& panel_bounds) {
+  const PanelManager::Panels& panels = PanelManager::GetInstance()->panels();
+  int offset_to_move_above_panels = 0;
+
+  // The offset is the maximum height of panels that could overlap with the
+  // balloons.
+  if (NeedToMoveAboveLeftSidePanels()) {
+    // If the affecting panel does not lie in the balloon area, no need to
+    // update the offset.
+    if (!panel_bounds.IsEmpty() &&
+        (panel_bounds.right() <= work_area_.x() ||
+         panel_bounds.x() >= work_area_.x() + max_balloon_width())) {
+      return false;
+    }
+
+    for (PanelManager::Panels::const_reverse_iterator iter = panels.rbegin();
+         iter != panels.rend(); ++iter) {
+      // No need to check panels beyond the area occupied by the balloons.
+      if ((*iter)->GetBounds().x() >= work_area_.x() + max_balloon_width())
+        break;
+
+      int current_height = (*iter)->GetBounds().height();
+      if (current_height > offset_to_move_above_panels)
+        offset_to_move_above_panels = current_height;
+    }
+  } else if (NeedToMoveAboveRightSidePanels()) {
+    // If the affecting panel does not lie in the balloon area, no need to
+    // update the offset.
+    if (!panel_bounds.IsEmpty() &&
+        (panel_bounds.right() <= work_area_.right() - max_balloon_width() ||
+         panel_bounds.x() >= work_area_.right())) {
+      return false;
+    }
+
+    for (PanelManager::Panels::const_iterator iter = panels.begin();
+         iter != panels.end(); ++iter) {
+      // No need to check panels beyond the area occupied by the balloons.
+      if ((*iter)->GetBounds().right() <=
+          work_area_.right() - max_balloon_width())
+        break;
+
+      int current_height = (*iter)->GetBounds().height();
+      if (current_height > offset_to_move_above_panels)
+        offset_to_move_above_panels = current_height;
+    }
+  }
+
+  // Ensure that we have some sort of margin between the 1st balloon and the
+  // panel beneath it even the vertical edge margin is 0 as on Mac.
+  if (offset_to_move_above_panels && !VerticalEdgeMargin())
+    offset_to_move_above_panels += kVerticalSpacingBetweenBalloonAndPanel;
+
+  // If no change is detected, return false to indicate that we do not need to
+  // reposition balloons.
+  if (offset_to_move_above_panels_ == offset_to_move_above_panels)
+    return false;
+
+  offset_to_move_above_panels_ = offset_to_move_above_panels;
+  return true;
+}
+
 bool BalloonCollectionImpl::Layout::RefreshSystemMetrics() {
   bool changed = false;
 
diff --git a/chrome/browser/notifications/balloon_collection_impl.h b/chrome/browser/notifications/balloon_collection_impl.h
index 887d1f2..424351c 100644
--- a/chrome/browser/notifications/balloon_collection_impl.h
+++ b/chrome/browser/notifications/balloon_collection_impl.h
@@ -16,6 +16,8 @@
 #include "base/message_loop.h"
 #include "chrome/browser/notifications/balloon_collection.h"
 #include "chrome/browser/notifications/balloon_collection_base.h"
+#include "content/public/browser/notification_observer.h"
+#include "content/public/browser/notification_registrar.h"
 #include "ui/gfx/point.h"
 #include "ui/gfx/rect.h"
 
@@ -32,7 +34,8 @@
 // shown on the screen.  It positions new notifications according to
 // a layout, and monitors for balloons being closed, which it reports
 // up to its parent, the notification UI manager.
-class BalloonCollectionImpl : public BalloonCollection
+class BalloonCollectionImpl : public BalloonCollection,
+                              public content::NotificationObserver
 #if USE_OFFSETS
                             , public MessageLoopForUI::Observer
 #endif
@@ -54,6 +57,11 @@ class BalloonCollectionImpl : public BalloonCollection
   virtual void OnBalloonClosed(Balloon* source);
   virtual const Balloons& GetActiveBalloons();
 
+  // content::NotificationObserver interface.
+  virtual void Observe(int type,
+                       const content::NotificationSource& source,
+                       const content::NotificationDetails& details) OVERRIDE;
+
   // MessageLoopForUI::Observer interface.
 #if defined(OS_WIN) || defined(TOUCH_UI) || defined(USE_AURA)
   virtual base::EventStatus WillProcessEvent(
@@ -127,12 +135,19 @@ class BalloonCollectionImpl : public BalloonCollection
     // buttons under the cursor during rapid-close interaction.
     bool RequiresOffsets() const;
 
+    // Returns true if there is change to the offset that requires the balloons
+    // to be repositioned.
+    bool ComputeOffsetToMoveAbovePanels(const gfx::Rect& panel_bounds);
+
    private:
     // Layout parameters
     int VerticalEdgeMargin() const;
     int HorizontalEdgeMargin() const;
     int InterBalloonMargin() const;
 
+    bool NeedToMoveAboveLeftSidePanels() const;
+    bool NeedToMoveAboveRightSidePanels() const;
+
     // Minimum and maximum size of balloon content.
     static const int kBalloonMinWidth = 300;
     static const int kBalloonMaxWidth = 300;
@@ -141,6 +156,12 @@ class BalloonCollectionImpl : public BalloonCollection
 
     Placement placement_;
     gfx::Rect work_area_;
+
+    // The offset that guarantees that the notificaitions shown in the
+    // lower-right or lower-left corner of the screen will go above currently
+    // shown panels and will not be obscured by them.
+    int offset_to_move_above_panels_;
+
     DISALLOW_COPY_AND_ASSIGN(Layout);
   };
 
@@ -171,6 +192,8 @@ class BalloonCollectionImpl : public BalloonCollection
   // The layout parameters for balloons in this collection.
   Layout layout_;
 
+  content::NotificationRegistrar registrar_;
+
 #if USE_OFFSETS
   // Start and stop observing all UI events.
   void AddMessageLoopObserver();
diff --git a/chrome/browser/notifications/balloon_collection_mac.mm b/chrome/browser/notifications/balloon_collection_mac.mm
index d31bc39..a30b689 100644
--- a/chrome/browser/notifications/balloon_collection_mac.mm
+++ b/chrome/browser/notifications/balloon_collection_mac.mm
@@ -1,4 +1,4 @@
-// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Copyright (c) 2011 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.
 
@@ -35,6 +35,14 @@ int BalloonCollectionImpl::Layout::VerticalEdgeMargin() const {
   return 0;
 }
 
+bool BalloonCollectionImpl::Layout::NeedToMoveAboveLeftSidePanels() const {
+  return placement_ == VERTICALLY_FROM_TOP_LEFT;
+}
+
+bool BalloonCollectionImpl::Layout::NeedToMoveAboveRightSidePanels() const {
+  return placement_ == VERTICALLY_FROM_TOP_RIGHT;
+}
+
 void BalloonCollectionImpl::PositionBalloons(bool reposition) {
   // Use an animation context so that all the balloons animate together.
   [NSAnimationContext beginGrouping];
@@ -61,6 +69,7 @@ void BalloonCollectionImpl::SetPositionPreference(
   else
     NOTREACHED();
 
+  layout_.ComputeOffsetToMoveAbovePanels(gfx::Rect());
   PositionBalloons(true);
 }
 
diff --git a/chrome/browser/notifications/balloon_collection_views.cc b/chrome/browser/notifications/balloon_collection_views.cc
index c436df88..f5ac0e4 100644
--- a/chrome/browser/notifications/balloon_collection_views.cc
+++ b/chrome/browser/notifications/balloon_collection_views.cc
@@ -31,6 +31,14 @@ int BalloonCollectionImpl::Layout::VerticalEdgeMargin() const {
   return 0;
 }
 
+bool BalloonCollectionImpl::Layout::NeedToMoveAboveLeftSidePanels() const {
+  return placement_ == VERTICALLY_FROM_BOTTOM_LEFT;
+}
+
+bool BalloonCollectionImpl::Layout::NeedToMoveAboveRightSidePanels() const {
+  return placement_ == VERTICALLY_FROM_BOTTOM_RIGHT;
+}
+
 void BalloonCollectionImpl::PositionBalloons(bool reposition) {
   PositionBalloonsInternal(reposition);
 }
@@ -96,6 +104,7 @@ void BalloonCollectionImpl::SetPositionPreference(
   else
     NOTREACHED();
 
+  layout_.ComputeOffsetToMoveAbovePanels(gfx::Rect());
   PositionBalloons(true);
 }
 
diff --git a/chrome/browser/ui/panels/base_panel_browser_test.cc b/chrome/browser/ui/panels/base_panel_browser_test.cc
index bcfbee0..992557b 100644
--- a/chrome/browser/ui/panels/base_panel_browser_test.cc
+++ b/chrome/browser/ui/panels/base_panel_browser_test.cc
@@ -148,6 +148,11 @@ void MockAutoHidingDesktopBarImpl::NotifyThicknessChange() {
   observer_->OnAutoHidingDesktopBarThicknessChanged();
 }
 
+bool ExistsPanel(Panel* panel) {
+  const PanelManager::Panels& panels = PanelManager::GetInstance()->panels();
+  return find(panels.begin(), panels.end(), panel) != panels.end();
+}
+
 }  // namespace
 
 BasePanelBrowserTest::BasePanelBrowserTest()
@@ -175,7 +180,10 @@ void BasePanelBrowserTest::SetUpOnMainThread() {
   mock_auto_hiding_desktop_bar_ = new MockAutoHidingDesktopBarImpl(
       panel_manager);
   panel_manager->set_auto_hiding_desktop_bar(mock_auto_hiding_desktop_bar_);
-  panel_manager->SetWorkAreaForTesting(testing_work_area_);
+  // Do not use the testing work area if it is empty since we're going to
+  // use the actual work area in some testing scenarios.
+  if (!testing_work_area_.IsEmpty())
+    panel_manager->SetWorkAreaForTesting(testing_work_area_);
   panel_manager->enable_auto_sizing(false);
   panel_manager->remove_delays_for_testing();
   // This is needed so the subsequently created panels can be activated.
@@ -183,6 +191,26 @@ void BasePanelBrowserTest::SetUpOnMainThread() {
   EXPECT_TRUE(ui_test_utils::BringBrowserWindowToFront(browser()));
 }
 
+void BasePanelBrowserTest::WaitForPanelAdded(Panel* panel) {
+  if (ExistsPanel(panel))
+    return;
+  ui_test_utils::WindowedNotificationObserver signal(
+      chrome::NOTIFICATION_PANEL_ADDED,
+      content::Source<Panel>(panel));
+  signal.Wait();
+  EXPECT_TRUE(ExistsPanel(panel));
+}
+
+void BasePanelBrowserTest::WaitForPanelRemoved(Panel* panel) {
+  if (!ExistsPanel(panel))
+    return;
+  ui_test_utils::WindowedNotificationObserver signal(
+      chrome::NOTIFICATION_PANEL_REMOVED,
+      content::Source<Panel>(panel));
+  signal.Wait();
+  EXPECT_FALSE(ExistsPanel(panel));
+}
+
 void BasePanelBrowserTest::WaitForPanelActiveState(
     Panel* panel, ActiveState expected_state) {
   DCHECK(expected_state == SHOW_AS_ACTIVE ||
diff --git a/chrome/browser/ui/panels/base_panel_browser_test.h b/chrome/browser/ui/panels/base_panel_browser_test.h
index 42cf7e0..a833706 100644
--- a/chrome/browser/ui/panels/base_panel_browser_test.h
+++ b/chrome/browser/ui/panels/base_panel_browser_test.h
@@ -58,6 +58,8 @@ class BasePanelBrowserTest : public InProcessBrowserTest {
                                const gfx::Rect& bounds);
   Panel* CreatePanel(const std::string& panel_name);
 
+  void WaitForPanelAdded(Panel* panel);
+  void WaitForPanelRemoved(Panel* panel);
   void WaitForPanelActiveState(Panel* panel, ActiveState state);
   void WaitForWindowSizeAvailable(Panel* panel);
   void WaitForBoundsAnimationFinished(Panel* panel);
@@ -69,6 +71,9 @@ class BasePanelBrowserTest : public InProcessBrowserTest {
                                            const DictionaryValue& extra_value);
 
   gfx::Rect testing_work_area() const { return testing_work_area_; }
+  void set_testing_work_area(const gfx::Rect& work_area) {
+    testing_work_area_ = work_area;
+  }
 
   MockAutoHidingDesktopBar* mock_auto_hiding_desktop_bar() const {
     return mock_auto_hiding_desktop_bar_.get();
diff --git a/chrome/browser/ui/panels/panel.cc b/chrome/browser/ui/panels/panel.cc
index b231136..976ede4 100644
--- a/chrome/browser/ui/panels/panel.cc
+++ b/chrome/browser/ui/panels/panel.cc
@@ -63,6 +63,11 @@ void Panel::SetPanelBounds(const gfx::Rect& bounds) {
     restored_height_ = bounds.height();
 
   native_panel_->SetPanelBounds(bounds);
+
+  content::NotificationService::current()->Notify(
+      chrome::NOTIFICATION_PANEL_CHANGED_BOUNDS,
+      content::Source<Panel>(this),
+      content::NotificationService::NoDetails());
 }
 
 void Panel::SetMaxSize(const gfx::Size& max_size) {
diff --git a/chrome/browser/ui/panels/panel_browsertest.cc b/chrome/browser/ui/panels/panel_browsertest.cc
index 382642c..8b146be 100644
--- a/chrome/browser/ui/panels/panel_browsertest.cc
+++ b/chrome/browser/ui/panels/panel_browsertest.cc
@@ -4,9 +4,16 @@
 
 #include "base/bind.h"
 #include "base/string_number_conversions.h"
+#include "base/utf_string_conversions.h"
+#include "chrome/browser/browser_process.h"
 #include "chrome/browser/download/download_service.h"
 #include "chrome/browser/download/download_service_factory.h"
 #include "chrome/browser/net/url_request_mock_util.h"
+#include "chrome/browser/notifications/balloon_collection_impl.h"
+#include "chrome/browser/notifications/desktop_notification_service.h"
+#include "chrome/browser/notifications/notification.h"
+#include "chrome/browser/notifications/notification_ui_manager.h"
+#include "chrome/browser/prefs/browser_prefs.h"
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/browser_list.h"
@@ -26,9 +33,11 @@
 #include "content/browser/download/download_manager.h"
 #include "content/browser/net/url_request_mock_http_job.h"
 #include "content/browser/tab_contents/tab_contents.h"
+#include "content/common/desktop_notification_messages.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/common/url_constants.h"
 #include "testing/gtest/include/gtest/gtest.h"
+#include "ui/gfx/screen.h"
 
 using content::BrowserThread;
 
@@ -1565,3 +1574,164 @@ IN_PROC_BROWSER_TEST_F(PanelDownloadTest, DownloadNoTabbedBrowser) {
 
   panel_browser->CloseWindow();
 }
+
+class PanelAndNotificationTest : public PanelBrowserTest {
+ public:
+  PanelAndNotificationTest() : PanelBrowserTest() {
+    // Do not use our own testing work area since desktop notification code
+    // does not have the hook up for testing work area.
+    set_testing_work_area(gfx::Rect());
+  }
+
+  virtual ~PanelAndNotificationTest() {
+  }
+
+  virtual void SetUpOnMainThread() OVERRIDE {
+    g_browser_process->local_state()->SetInteger(
+        prefs::kDesktopNotificationPosition, BalloonCollection::LOWER_RIGHT);
+    balloons_ = new BalloonCollectionImpl();
+    ui_manager_.reset(NotificationUIManager::Create(
+        g_browser_process->local_state(), balloons_));
+    service_.reset(new DesktopNotificationService(browser()->profile(),
+                   ui_manager_.get()));
+
+    PanelBrowserTest::SetUpOnMainThread();
+  }
+
+  virtual void CleanUpOnMainThread() OVERRIDE {
+    balloons_->RemoveAll();
+    MessageLoopForUI::current()->RunAllPending();
+
+    service_.reset();
+    ui_manager_.reset();
+
+    PanelBrowserTest::CleanUpOnMainThread();
+  }
+
+  DesktopNotificationHostMsg_Show_Params StandardTestNotification() {
+    DesktopNotificationHostMsg_Show_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");
+    params.direction = WebKit::WebTextDirectionDefault;
+    return params;
+  }
+
+  int GetBalloonBottomPosition(Balloon* balloon) const {
+#if defined(OS_MACOSX)
+    // The position returned by the notification balloon is based on Mac's
+    // vertically inverted orientation. We need to flip it so that it can
+    // be compared against the position returned by the panel.
+    gfx::Size screen_size = gfx::Screen::GetPrimaryMonitorSize();
+    return screen_size.height() - balloon->GetPosition().y();
+#else
+    return balloon->GetPosition().y() + balloon->GetViewSize().height();
+#endif
+  }
+
+  DesktopNotificationService* service() const { return service_.get(); }
+  const BalloonCollection::Balloons& balloons() const {
+    return balloons_->GetActiveBalloons();
+  }
+
+ private:
+  BalloonCollectionImpl* balloons_;  // Owned by NotificationUIManager.
+  scoped_ptr<NotificationUIManager> ui_manager_;
+  scoped_ptr<DesktopNotificationService> service_;
+};
+
+IN_PROC_BROWSER_TEST_F(PanelAndNotificationTest, NoOverlapping) {
+  const int kPanelWidth = 200;
+  const int kShortPanelHeight = 150;
+  const int kTallPanelHeight = 200;
+
+  DesktopNotificationHostMsg_Show_Params params = StandardTestNotification();
+  EXPECT_TRUE(service()->ShowDesktopNotification(
+        params, 0, 0, DesktopNotificationService::PageNotification));
+  MessageLoopForUI::current()->RunAllPending();
+  Balloon* balloon = balloons().front();
+  int original_balloon_bottom = GetBalloonBottomPosition(balloon);
+  // Ensure that balloon width is greater than the panel width.
+  EXPECT_GT(balloon->GetViewSize().width(), kPanelWidth);
+
+  // Creating a short panel should move the notification balloon up.
+  Panel* panel1 = CreatePanelWithBounds(
+      "Panel1", gfx::Rect(0, 0, kPanelWidth, kShortPanelHeight));
+  WaitForPanelAdded(panel1);
+  int balloon_bottom_after_short_panel_created =
+      GetBalloonBottomPosition(balloon);
+  EXPECT_LT(balloon_bottom_after_short_panel_created, panel1->GetBounds().y());
+  EXPECT_LT(balloon_bottom_after_short_panel_created, original_balloon_bottom);
+
+  // Creating another tall panel should move the notification balloon further
+  // up.
+  Panel* panel2 = CreatePanelWithBounds(
+      "Panel2", gfx::Rect(0, 0, kPanelWidth, kTallPanelHeight));
+  WaitForPanelAdded(panel2);
+  int balloon_bottom_after_tall_panel_created =
+      GetBalloonBottomPosition(balloon);
+  EXPECT_LT(balloon_bottom_after_tall_panel_created, panel2->GetBounds().y());
+  EXPECT_LT(balloon_bottom_after_tall_panel_created,
+            balloon_bottom_after_short_panel_created);
+
+  // Minimizing tall panel should move the notification balloon down to the same
+  // position when short panel is first created.
+  panel2->SetExpansionState(Panel::MINIMIZED);
+  WaitForBoundsAnimationFinished(panel2);
+  int balloon_bottom_after_tall_panel_minimized =
+      GetBalloonBottomPosition(balloon);
+  EXPECT_EQ(balloon_bottom_after_short_panel_created,
+            balloon_bottom_after_tall_panel_minimized);
+
+  // Minimizing short panel should move the notification balloon further down.
+  panel1->SetExpansionState(Panel::MINIMIZED);
+  WaitForBoundsAnimationFinished(panel1);
+  int balloon_bottom_after_both_panels_minimized =
+      GetBalloonBottomPosition(balloon);
+  EXPECT_LT(balloon_bottom_after_both_panels_minimized,
+            panel1->GetBounds().y());
+  EXPECT_LT(balloon_bottom_after_both_panels_minimized,
+            panel2->GetBounds().y());
+  EXPECT_LT(balloon_bottom_after_short_panel_created,
+            balloon_bottom_after_both_panels_minimized);
+  EXPECT_LT(balloon_bottom_after_both_panels_minimized,
+            original_balloon_bottom);
+
+  // Bringing up the titlebar for tall panel should move the notification
+  // balloon up a little bit.
+  panel2->SetExpansionState(Panel::TITLE_ONLY);
+  WaitForBoundsAnimationFinished(panel2);
+  int balloon_bottom_after_tall_panel_titlebar_up =
+      GetBalloonBottomPosition(balloon);
+  EXPECT_LT(balloon_bottom_after_tall_panel_titlebar_up,
+            panel2->GetBounds().y());
+  EXPECT_LT(balloon_bottom_after_tall_panel_titlebar_up,
+            balloon_bottom_after_both_panels_minimized);
+  EXPECT_LT(balloon_bottom_after_short_panel_created,
+            balloon_bottom_after_tall_panel_titlebar_up);
+
+  // Expanding short panel should move the notification balloon further up to
+  // the same position when short panel is first created.
+  panel1->SetExpansionState(Panel::EXPANDED);
+  WaitForBoundsAnimationFinished(panel1);
+  int balloon_bottom_after_short_panel_expanded =
+      GetBalloonBottomPosition(balloon);
+  EXPECT_EQ(balloon_bottom_after_short_panel_created,
+            balloon_bottom_after_short_panel_expanded);
+
+  // Closing short panel should move the notification balloon down to the same
+  // position when tall panel brings up its titlebar.
+  panel1->Close();
+  WaitForBoundsAnimationFinished(panel1);
+  EXPECT_EQ(balloon_bottom_after_tall_panel_titlebar_up,
+            GetBalloonBottomPosition(balloon));
+
+  // Closing the remaining tall panel should move the notification balloon back
+  // to its original position.
+  panel2->Close();
+  WaitForBoundsAnimationFinished(panel2);
+  EXPECT_EQ(original_balloon_bottom, GetBalloonBottomPosition(balloon));
+}
diff --git a/chrome/browser/ui/panels/panel_manager.cc b/chrome/browser/ui/panels/panel_manager.cc
index 0f4c0d2..e37eb43 100644
--- a/chrome/browser/ui/panels/panel_manager.cc
+++ b/chrome/browser/ui/panels/panel_manager.cc
@@ -13,6 +13,9 @@
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_list.h"
 #include "chrome/browser/ui/window_sizer.h"
+#include "chrome/common/chrome_notification_types.h"
+#include "content/public/browser/notification_service.h"
+#include "content/public/browser/notification_source.h"
 
 namespace {
 // Invalid panel index.
@@ -120,6 +123,12 @@ Panel* PanelManager::CreatePanel(Browser* browser) {
   Panel* panel = new Panel(browser, gfx::Rect(x, y, width, height));
   panel->SetMaxSize(gfx::Size(max_panel_width, max_panel_height));
   panels_.push_back(panel);
+
+  content::NotificationService::current()->Notify(
+      chrome::NOTIFICATION_PANEL_ADDED,
+      content::Source<Panel>(panel),
+      content::NotificationService::NoDetails());
+
   return panel;
 }
 
@@ -166,6 +175,11 @@ void PanelManager::DoRemove(Panel* panel) {
 
   gfx::Rect bounds = (*iter)->GetBounds();
   Rearrange(panels_.erase(iter), bounds.right());
+
+  content::NotificationService::current()->Notify(
+      chrome::NOTIFICATION_PANEL_REMOVED,
+      content::Source<Panel>(panel),
+      content::NotificationService::NoDetails());
 }
 
 void PanelManager::StartDragging(Panel* panel) {
diff --git a/chrome/browser/ui/panels/panel_manager.h b/chrome/browser/ui/panels/panel_manager.h
index 7b272ab6c..0e0d3cb 100644
--- a/chrome/browser/ui/panels/panel_manager.h
+++ b/chrome/browser/ui/panels/panel_manager.h
@@ -73,6 +73,7 @@ class PanelManager : public PanelMouseWatcher::Observer,
 
   int num_panels() const { return panels_.size(); }
   bool is_dragging_panel() const;
+  const Panels& panels() const { return panels_; }
 
   int GetMaxPanelWidth() const;
   int GetMaxPanelHeight() const;
@@ -82,7 +83,6 @@ class PanelManager : public PanelMouseWatcher::Observer,
   virtual void OnMouseMove(const gfx::Point& mouse_position) OVERRIDE;
 
 #ifdef UNIT_TEST
-  const Panels& panels() const { return panels_; }
   static int horizontal_spacing() { return kPanelsHorizontalSpacing; }
 
   const gfx::Rect& work_area() const {
diff --git a/chrome/common/chrome_notification_types.h b/chrome/common/chrome_notification_types.h
index 12477c3..e2467d8 100644
--- a/chrome/common/chrome_notification_types.h
+++ b/chrome/common/chrome_notification_types.h
@@ -947,6 +947,21 @@ enum NotificationType {
   // Used only in unit testing.
   NOTIFICATION_PANEL_WINDOW_SIZE_KNOWN,
 
+  // Sent when panel's bounds get changed.
+  // The source is the Panel, no details.
+  // Used only in coordination with notification balloons.
+  NOTIFICATION_PANEL_CHANGED_BOUNDS,
+
+  // Sent when panel is added into the panel manager.
+  // The source is the Panel, no details.
+  // Used only in coordination with notification balloons.
+  NOTIFICATION_PANEL_ADDED,
+
+  // Sent when panel is removed from the panel manager.
+  // The source is the Panel, no details.
+  // Used only in coordination with notification balloons.
+  NOTIFICATION_PANEL_REMOVED,
+
   // Sent when a global error has changed and the error UI should update it
   // self. The source is a Source<Profile> containing the profile for the
   // error. The detail is a GlobalError object that has changed or NULL if