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

chrome/browser/ui/views/frame/browser_frame_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 "chrome/browser/ui/views/frame/browser_frame_mac.h"
 
 #include "chrome/browser/ui/views/frame/browser_frame.h"
 #include "chrome/browser/ui/views/frame/browser_shutdown.h"
 #include "chrome/browser/ui/views/frame/browser_view.h"
 #import "chrome/browser/ui/views/frame/native_widget_mac_frameless_nswindow.h"
@@ skipping 29 matching lines @@
   NSView* content_view = [GetNativeWindow() contentView];
   NSView* root_view = [content_view superview];
   [content_view removeFromSuperview];
   [root_view setWantsLayer:YES];
   [root_view addSubview:content_view positioned:NSWindowBelow relativeTo:nil];
 }
 
 gfx::NativeWindow BrowserFrameMac::CreateNSWindow(
     const views::Widget::InitParams& params) {
   NSUInteger style_mask = NSTitledWindowMask | NSClosableWindowMask |
-                          NSMiniaturizableWindowMask | NSResizableWindowMask;
+                          NSMiniaturizableWindowMask | NSResizableWindowMask |
+                          NSTexturedBackgroundWindowMask;
   return [[[NativeWidgetMacFramelessNSWindow alloc]
       initWithContentRect:ui::kWindowSizeDeterminedLater
                 styleMask:style_mask
                   backing:NSBackingStoreBuffered
                     defer:YES] autorelease];
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // BrowserFrameMac, NativeBrowserFrame implementation:
 
@@ skipping 18 matching lines @@
 void BrowserFrameMac::GetWindowPlacement(
     gfx::Rect* bounds,
     ui::WindowShowState* show_state) const {
   return NativeWidgetMac::GetWindowPlacement(bounds, show_state);
 }
 
 int BrowserFrameMac::GetMinimizeButtonOffset() const {
   NOTIMPLEMENTED();
   return 0;
 }