Support detaching/attaching panels via inter-strip drags.

chrome/browser/ui/panels/panel_window_controller_cocoa.mm

Index: chrome/browser/ui/panels/panel_window_controller_cocoa.mm
diff --git a/chrome/browser/ui/panels/panel_window_controller_cocoa.mm b/chrome/browser/ui/panels/panel_window_controller_cocoa.mm
index 0576fcc44e54af4f10e9998d34e6f4f19f9a4df6..bdcbbbf24e4c1aaefd29e891c80e2eb4655eea97 100644
--- a/chrome/browser/ui/panels/panel_window_controller_cocoa.mm
+++ b/chrome/browser/ui/panels/panel_window_controller_cocoa.mm
@@ -80,6 +80,7 @@ enum {
   if ((self = [super initWithWindowNibPath:nibpath owner:self])) {
     windowShim_.reset(window);
     animateOnBoundsChange_ = YES;
+    alwaysOnTop_ = YES;
   }
   contentsController_.reset(
       [[TabContentsController alloc] initWithContents:nil]);
@@ -117,8 +118,7 @@ enum {
   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:
@@ -634,8 +634,7 @@ enum {
 }
 
 - (void)fullScreenModeChanged:(bool)isFullScreen {
-  NSWindow* window = [self window];
-  [window setLevel:(isFullScreen ? NSNormalWindowLevel : NSStatusWindowLevel)];
+  [self updateWindowLevel];
 }
 
 - (BOOL)canBecomeKeyWindow {
@@ -646,4 +645,19 @@ enum {
   // cases when minimized Panel is getting keyboard input, invisibly.
   return windowShim_->panel()->expansion_state() == Panel::EXPANDED;
 }
+
+- (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