[MacViews] Enable dragging a window by its caption/draggable areas.

ui/views/widget/native_widget_mac.mm

 // Copyright 2014 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 "ui/views/widget/native_widget_mac.h"
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/mac/foundation_util.h"
 #include "base/mac/scoped_nsobject.h"
@@ skipping 26 matching lines @@
 namespace views {
 namespace {
 
 NSInteger StyleMaskForParams(const Widget::InitParams& params) {
   // TODO(tapted): Determine better masks when there are use cases for it.
   if (params.remove_standard_frame)
     return NSBorderlessWindowMask;
 
   if (params.type == Widget::InitParams::TYPE_WINDOW) {
     return NSTitledWindowMask | NSClosableWindowMask |
-           NSMiniaturizableWindowMask | NSResizableWindowMask;
+           NSMiniaturizableWindowMask | NSResizableWindowMask |
+           NSTexturedBackgroundWindowMask;
   }
   return NSBorderlessWindowMask;
 }
 
 }  // namespace
 
 ////////////////////////////////////////////////////////////////////////////////
 // NativeWidgetMac, public:
 
 NativeWidgetMac::NativeWidgetMac(internal::NativeWidgetDelegate* delegate)
@@ skipping 631 matching lines @@
   [[ViewsNSWindowCloseAnimator alloc] initWithWindow:window];
 }
 
 - (void)animationDidEnd:(NSAnimation*)animation {
   [window_ close];
   [animation_ setDelegate:nil];
   [self release];
 }
 
 @end