Refactor ViewsDelegate singleton

ui/views/window/custom_frame_view.cc

 // 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 "ui/views/window/custom_frame_view.h"
 
 #include <algorithm>
 #include <vector>
 
 #include "base/strings/utf_string_conversions.h"
@@ skipping 315 matching lines @@
   int y = unavailable_px_at_top + (NonClientTopBorderHeight() -
       unavailable_px_at_top - size - TitlebarBottomThickness() + 1) / 2;
   return gfx::Rect(frame_thickness + kIconLeftSpacing + minimum_title_bar_x_,
                    y, size, size);
 }
 
 bool CustomFrameView::ShouldShowTitleBarAndBorder() const {
   if (frame_->IsFullscreen())
     return false;
 
-  if (ViewsDelegate::views_delegate) {
-    return !ViewsDelegate::views_delegate->WindowManagerProvidesTitleBar(
-                frame_->IsMaximized());
+  if (ViewsDelegate::GetInstance()) {
+    return !ViewsDelegate::GetInstance()->WindowManagerProvidesTitleBar(
+        frame_->IsMaximized());
   }
 
   return true;
 }
 
 bool CustomFrameView::ShouldShowClientEdge() const {
   return !frame_->IsMaximized() && ShouldShowTitleBarAndBorder();
 }
 
 void CustomFrameView::PaintRestoredFrameBorder(gfx::Canvas* canvas) {
@@ skipping 274 matching lines @@
     }
     case views::FRAME_BUTTON_CLOSE: {
       button = close_button_;
       break;
     }
   }
   return button;
 }
 
 }  // namespace views