Add always-on-top property to app windows

chrome/browser/ui/cocoa/browser_window_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/cocoa/browser_window_cocoa.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/mac/mac_util.h"
@@ skipping 241 matching lines @@
   } else {
     [NSApp cancelUserAttentionRequest:attention_request_id_];
     attention_request_id_ = 0;
   }
 }
 
 bool BrowserWindowCocoa::IsAlwaysOnTop() const {
   return false;
 }
 
+void BrowserWindowCocoa::SetAlwaysOnTop(bool always_on_top) {
+  // Not implemented for browser windows.
+  NOTIMPLEMENTED();
+}
+
 bool BrowserWindowCocoa::IsActive() const {
   return [window() isKeyWindow];
 }
 
 gfx::NativeWindow BrowserWindowCocoa::GetNativeWindow() {
   return window();
 }
 
 BrowserWindowTesting* BrowserWindowCocoa::GetBrowserWindowTesting() {
   return NULL;
@@ skipping 501 matching lines @@
   // further, both by another H, i.e. WebContentsView's height becomes
   // A.height() + H and RenderWidgetHostView's height becomes A.height() + 2H.
   // Strangely, the RenderWidgetHostView for the previous navigation entry also
   // gets enlarged by H.
   // I believe these "automatic" resizing are caused by setAutoresizingMask of
   // of the cocoa view in WebContentsViewMac, which defeats the purpose of
   // WebContentsDelegate::GetSizeForNewRenderView i.e. to prevent resizing of
   // RenderWidgetHostView in (2) and (3).
   return 0;
 }