Add support for observing tracking areas so that when tabs are moved undernea...

chrome/browser/cocoa/tab_strip_controller.mm

Index: chrome/browser/cocoa/tab_strip_controller.mm
===================================================================
--- chrome/browser/cocoa/tab_strip_controller.mm	(revision 31786)
+++ chrome/browser/cocoa/tab_strip_controller.mm	(working copy)
@@ -107,6 +107,7 @@
 - (void)animationDidStopForController:(TabController*)controller
                              finished:(BOOL)finished;
 - (NSInteger)indexFromModelIndex:(NSInteger)index;
+- (void)mouseMoved:(NSEvent*)event;
 @end
 
 // A simple view class that prevents the Window Server from dragging the area
@@ -892,8 +893,15 @@
   // tell us what to swap in in its absence.
   [tabContentsArray_ removeObjectAtIndex:index];
 
+  NSView* tab = [controller view];
+
+  // Stop observing the tab's tracking areas.
+  NSNotificationCenter* defaultCenter = [NSNotificationCenter defaultCenter];
+  [defaultCenter removeObserver:self
+                           name:NSViewDidUpdateTrackingAreasNotification
+                         object:tab];
+
   // Remove the view from the tab strip.
-  NSView* tab = [controller view];
   [tab removeFromSuperview];
 
   // Clear the tab controller's target.
@@ -1183,6 +1191,27 @@
   [self layoutTabsWithAnimation:NO regenerateSubviews:NO];
 }
 
+// Called when the tracking areas for any given tab are updated. This allows
+// the individual tabs to update their hover states correctly.
+// Only generates the event if the cursor is in the tab strip.
+- (void)tabUpdateTracking:(NSNotification*)notification {
+  DCHECK([[notification object] isKindOfClass:[TabView class]]);
+  NSWindow* window = [tabView_ window];
+  NSPoint location = [window mouseLocationOutsideOfEventStream];
+  if (NSPointInRect(location, [tabView_ frame])) {
+    NSEvent* mouseEvent = [NSEvent mouseEventWithType:NSMouseMoved
+                                             location:location
+                                        modifierFlags:0
+                                            timestamp:0
+                                         windowNumber:[window windowNumber]
+                                              context:nil
+                                          eventNumber:0
+                                           clickCount:0
+                                             pressure:0];
+    [self mouseMoved:mouseEvent];
+  }
+}
+
 - (BOOL)inRapidClosureMode {
   return availableResizeWidth_ != kUseFullAvailableWidth;
 }
@@ -1252,6 +1281,15 @@
 // should call |-addSubviewToPermanentList:| (or better yet, call that and then
 // |-regenerateSubviewList| to actually add it).
 - (void)regenerateSubviewList {
+  // Remove self as an observer from all the old tabs before a new set of
+  // potentially different tabs is put in place.
+  NSNotificationCenter* defaultCenter = [NSNotificationCenter defaultCenter];
+  for (NSView* view in [tabView_ subviews]) {
+    [defaultCenter removeObserver:self
+                             name:NSViewDidUpdateTrackingAreasNotification
+                           object:view];
+  }
+
   // Subviews to put in (in bottom-to-top order), beginning with the permanent
   // ones.
   NSMutableArray* subviews = [NSMutableArray arrayWithArray:permanentSubviews_];
@@ -1259,11 +1297,19 @@
   NSView* selectedTabView = nil;
   // Go through tabs in reverse order, since |subviews| is bottom-to-top.
   for (TabController* tab in [tabArray_.get() reverseObjectEnumerator]) {
+    NSView* tabView = [tab view];
+
+    // Set self up to observe tabs so hover states will be correct as tabs move.
+    [defaultCenter addObserver:self
+                      selector:@selector(tabUpdateTracking:)
+                          name:NSViewDidUpdateTrackingAreasNotification
+                        object:tabView];
+
     if ([tab selected]) {
       DCHECK(!selectedTabView);
-      selectedTabView = [tab view];
+      selectedTabView = tabView;
     } else {
-      [subviews addObject:[tab view]];
+      [subviews addObject:tabView];
     }
   }
   if (selectedTabView)