Implement 3-stage minimize animation for Panels on OSX.

chrome/browser/ui/panels/panel_titlebar_view_cocoa.mm

 // 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.
 
 #import "chrome/browser/ui/panels/panel_titlebar_view_cocoa.h"
 
 #include <Carbon/Carbon.h>  // kVK_Escape
 #import <Cocoa/Cocoa.h>
 
 #include "base/logging.h"
@@ skipping 194 matching lines @@
   NSImage* image = gfx::GetCachedImageWithName(@"balloon_wrench.pdf");
   [settingsButton_ setDefaultImage:image];
   [settingsButton_ setDefaultOpacity:0.6];
   [settingsButton_ setHoverImage:image];
   [settingsButton_ setHoverOpacity:0.9];
   [settingsButton_ setPressedImage:image];
   [settingsButton_ setPressedOpacity:1.0];
   [[settingsButton_ cell] setHighlightsBy:NSNoCellMask];
   [self checkMouseAndUpdateSettingsButtonVisibility];
 
-  // Update layout of controls in the titlebar.
   [self updateCloseButtonLayout];
 
   // Set autoresizing behavior: glued to edges on left, top and right.
   [self setAutoresizingMask:(NSViewMinYMargin | NSViewWidthSizable)];
 
   [[NSNotificationCenter defaultCenter]
       addObserver:self
          selector:@selector(didChangeTheme:)
              name:kBrowserThemeDidChangeNotification
            object:nil];
@@ skipping 31 matching lines @@
 
 - (NSView*)icon {
   return icon_;
 }
 
 - (void)updateCloseButtonLayout {
   NSRect buttonFrame = [closeButton_ frame];
   NSRect bounds = [self bounds];
 
   buttonFrame.origin.x = kButtonPadding;
-  buttonFrame.origin.y = (NSHeight(bounds) - NSHeight(buttonFrame)) / 2;
+  // Lower Close Button's frame 1 px to avoid it 'peeking' in MINIMIZED mode.
+  buttonFrame.origin.y = (NSHeight(bounds) - NSHeight(buttonFrame)) / 2 - 1;
   [closeButton_ setFrame:buttonFrame];
-
-  DCHECK(!closeButtonTrackingArea_.get());
-  closeButtonTrackingArea_.reset(
-      [[CrTrackingArea alloc] initWithRect:buttonFrame
-                                   options:(NSTrackingMouseEnteredAndExited |
-                                            NSTrackingActiveAlways)
-                              proxiedOwner:self
-                                  userInfo:nil]);
-  NSWindow* panelWindow = [self window];
-  [closeButtonTrackingArea_.get() clearOwnerWhenWindowWillClose:panelWindow];
-  [self addTrackingArea:closeButtonTrackingArea_.get()];
+  if (!closeButtonTrackingArea_.get()) {
+    closeButtonTrackingArea_.reset(
+        [[CrTrackingArea alloc] initWithRect:[closeButton_ bounds]
+                                     options:(NSTrackingMouseEnteredAndExited |
+                                              NSTrackingActiveAlways)
+                                proxiedOwner:self
+                                    userInfo:nil]);
+    NSWindow* panelWindow = [self window];
+    [closeButtonTrackingArea_.get() clearOwnerWhenWindowWillClose:panelWindow];
+    [closeButton_ addTrackingArea:closeButtonTrackingArea_.get()];
+  }
 }
 
 - (void)updateIconAndTitleLayout {
   NSRect closeButtonFrame = [closeButton_ frame];
   NSRect iconFrame = [icon_ frame];
   [title_ sizeToFit];
   NSRect titleFrame = [title_ frame];
   NSRect settingsButtonFrame = [settingsButtonWrapper_ frame];
   NSRect bounds = [self bounds];
 
@@ skipping 207 matching lines @@
 }
 
 - (void)checkMouseAndUpdateSettingsButtonVisibility {
   BOOL mouseOverWindow = NSPointInRect([NSEvent mouseLocation],
                                        [[self window] frame]);
   [self updateSettingsButtonVisibility:mouseOverWindow];
 }
 
 @end