Support detaching/attaching panels via inter-strip drags.

chrome/browser/ui/panels/panel_window_controller_cocoa.mm

 // Copyright (c) 2012 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/panels/panel_window_controller_cocoa.h"
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/logging.h"
 #include "base/mac/bundle_locations.h"
@@ skipping 63 matching lines @@
 
 @implementation PanelWindowControllerCocoa
 
 - (id)initWithBrowserWindow:(PanelBrowserWindowCocoa*)window {
   NSString* nibpath =
       [base::mac::FrameworkBundle() pathForResource:@"Panel" ofType:@"nib"];
   if ((self = [super initWithWindowNibPath:nibpath owner:self])) {
     windowShim_.reset(window);
     animateOnBoundsChange_ = YES;
     canBecomeKeyWindow_ = YES;
+    alwaysOnTop_ = YES;
   }
   contentsController_.reset(
       [[TabContentsController alloc] initWithContents:nil]);
   return self;
 }
 
 - (void)dealloc {
   if (windowTrackingArea_.get()) {
     [[[[self window] contentView] superview]
         removeTrackingArea:windowTrackingArea_.get()];
@@ skipping 17 matching lines @@
   return [BrowserWindowUtils themePatternPhaseFor:windowView withTabStrip:nil];
 }
 
 - (void)awakeFromNib {
   NSWindow* window = [self window];
 
   DCHECK(window);
   DCHECK(titlebar_view_);
   DCHECK_EQ(self, [window delegate]);
 
-  if (!windowShim_->panel()->manager()->is_full_screen())
-    [window setLevel:NSStatusWindowLevel];
+  [self updateWindowLevel];
 
   if (base::mac::IsOSSnowLeopardOrLater()) {
     [window setCollectionBehavior:
         NSWindowCollectionBehaviorParticipatesInCycle];
   }
 
   [titlebar_view_ attach];
 
   // Set initial size of the window to match the size of the panel to give
   // the renderer the proper size to work with earlier, avoiding a resize
@@ skipping 497 matching lines @@
     browser_window->Activate();
   else
     [NSApp deactivate];
 }
 
 - (void)preventBecomingKeyWindow:(BOOL)prevent {
   canBecomeKeyWindow_ = !prevent;
 }
 
 - (void)fullScreenModeChanged:(bool)isFullScreen {
-  NSWindow* window = [self window];
-  [window setLevel:(isFullScreen ? NSNormalWindowLevel : NSStatusWindowLevel)];
+  [self updateWindowLevel];
 }
 
 - (BOOL)canBecomeKeyWindow {
   // Panel can only gain focus if it is expanded. Minimized panels do not
   // participate in Cmd-~ rotation.
   // TODO(dimich): If it will be ever desired to expand/focus the Panel on
   // keyboard navigation or via main menu, the care should be taken to avoid
   // cases when minimized Panel is getting keyboard input, invisibly.
   return canBecomeKeyWindow_;
 }
 
+- (void)setAlwaysOnTop:(bool)onTop {
+  if (alwaysOnTop_ == onTop)
+    return;
+  alwaysOnTop_ = onTop;
+  [self updateWindowLevel];
+}
+
+- (void)updateWindowLevel {
+  if (![self isWindowLoaded])
+    return;
+  BOOL onTop = alwaysOnTop_ &&
+               !windowShim_->panel()->manager()->is_full_screen();
+  [[self window] setLevel:(onTop ? NSStatusWindowLevel : NSNormalWindowLevel)];
+}
 @end