Always set NSTexturedBackgroundWindowMask on app windows.

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

 // Copyright 2013 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.
 
 #ifndef CHROME_BROWSER_UI_COCOA_APPS_NATIVE_APP_WINDOW_COCOA_H_
 #define CHROME_BROWSER_UI_COCOA_APPS_NATIVE_APP_WINDOW_COCOA_H_
 
 #import <Cocoa/Cocoa.h>
 #include <vector>
 
@@ skipping 150 matching lines @@
   virtual void RemoveObserver(
       web_modal::ModalDialogHostObserver* observer) OVERRIDE;
 
  private:
   virtual ~NativeAppWindowCocoa();
 
   ShellNSWindow* window() const;
   content::WebContents* WebContents() const;
 
   // Returns the WindowStyleMask based on the type of window frame.
-  // Specifically, this includes NSResizableWindowMask if the window is
-  // resizable, and does not include NSTexturedBackgroundWindowMask when a
-  // native frame is used.
+  // This includes NSResizableWindowMask if the window is resizable.
   NSUInteger GetWindowStyleMask() const;
 
   void InstallView();
   void UninstallView();
   void UpdateDraggableRegionViews();
 
   // Cache |restored_bounds_| only if the window is currently restored.
   void UpdateRestoredBounds();
 
   // Hides the window unconditionally. Used by Hide and HideWithApp.
@@ skipping 25 matching lines @@
   std::vector<extensions::DraggableRegion> draggable_regions_;
 
   // The Extension Command Registry used to determine which keyboard events to
   // handle.
   scoped_ptr<ExtensionKeybindingRegistryCocoa> extension_keybinding_registry_;
 
   DISALLOW_COPY_AND_ASSIGN(NativeAppWindowCocoa);
 };
 
 #endif  // CHROME_BROWSER_UI_COCOA_APPS_NATIVE_APP_WINDOW_COCOA_H_