Add always-on-top property to app windows

chrome/browser/ui/cocoa/apps/native_app_window_cocoa.mm

Index: chrome/browser/ui/cocoa/apps/native_app_window_cocoa.mm
diff --git a/chrome/browser/ui/cocoa/apps/native_app_window_cocoa.mm b/chrome/browser/ui/cocoa/apps/native_app_window_cocoa.mm
index 5023194f69e6bef61035757bee43c1f89f74653a..fd18e0ce06d7c37e9b9359641c466d0f4382a78d 100644
--- a/chrome/browser/ui/cocoa/apps/native_app_window_cocoa.mm
+++ b/chrome/browser/ui/cocoa/apps/native_app_window_cocoa.mm
@@ -265,6 +265,12 @@ void SetFullScreenCollectionBehavior(NSWindow* window, bool allow_fullscreen) {
 - (void)setMouseDownCanMoveWindow:(BOOL)can_move;
 @end
 
+namespace {
+
+const NSInteger kAlwaysOnTopWindowLevel = NSFloatingWindowLevel;
+
+}  // namespace
+
 NativeAppWindowCocoa::NativeAppWindowCocoa(
     ShellWindow* shell_window,
     const ShellWindow::CreateParams& params)
@@ -334,6 +340,9 @@ NativeAppWindowCocoa::NativeAppWindowCocoa(
       [window respondsToSelector:@selector(setBottomCornerRounded:)])
     [window setBottomCornerRounded:NO];
 
+  if (params.always_on_top)
+    [window setLevel:kAlwaysOnTopWindowLevel];
+
   // Set the window to participate in Lion Fullscreen mode. Setting this flag
   // has no effect on Snow Leopard or earlier. UI controls for fullscreen are
   // only shown for apps that have unbounded size.
@@ -810,7 +819,7 @@ void NativeAppWindowCocoa::FlashFrame(bool flash) {
 }
 
 bool NativeAppWindowCocoa::IsAlwaysOnTop() const {
-  return false;
+  return [window() level] == kAlwaysOnTopWindowLevel;
 }
 
 void NativeAppWindowCocoa::RenderViewHostChanged(
@@ -986,6 +995,12 @@ void NativeAppWindowCocoa::ShowWithApp() {
   shell_window_->OnNativeWindowChanged();
 }
 
+void NativeAppWindowCocoa::SetAlwaysOnTop(bool always_on_top) {
+  [window() setLevel:(always_on_top ? kAlwaysOnTopWindowLevel :
+                                      NSNormalWindowLevel)];
+  shell_window_->OnNativeWindowChanged();
+}
+
 void NativeAppWindowCocoa::HideWithoutMarkingHidden() {
   [window() orderOut:window_controller_];
 }