MacViews: Add native drop shadow to dialogs on OSX < 10.10.

ui/views/window/dialog_delegate.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/dialog_delegate.h"
 
 #include <utility>
 
 #include "base/logging.h"
 #include "build/build_config.h"
@@ skipping 182 matching lines @@
     return CreateDialogFrameView(widget);
   return WidgetDelegate::CreateNonClientFrameView(widget);
 }
 
 // static
 NonClientFrameView* DialogDelegate::CreateDialogFrameView(Widget* widget) {
   BubbleFrameView* frame =
       new BubbleFrameView(gfx::Insets(kPanelVertMargin, kButtonHEdgeMarginNew,
                                       0, kButtonHEdgeMarginNew),
                           gfx::Insets());
-#if defined(OS_MACOSX)
-  // On Mac, dialogs have no border stroke and use a shadow provided by the OS.
-  const BubbleBorder::Shadow kShadow = BubbleBorder::NO_ASSETS;
-#else
   const BubbleBorder::Shadow kShadow = BubbleBorder::SMALL_SHADOW;
-#endif
   scoped_ptr<BubbleBorder> border(
       new BubbleBorder(BubbleBorder::FLOAT, kShadow, gfx::kPlaceholderColor));
   border->set_use_theme_background_color(true);
   frame->SetBubbleBorder(std::move(border));
   DialogDelegate* delegate = widget->widget_delegate()->AsDialogDelegate();
   if (delegate) {
     frame->SetTitlebarExtraView(
         make_scoped_ptr(delegate->CreateTitlebarExtraView()));
   }
   return frame;
@@ skipping 46 matching lines @@
   state->role = ui::AX_ROLE_DIALOG;
 }
 
 void DialogDelegateView::ViewHierarchyChanged(
     const ViewHierarchyChangedDetails& details) {
   if (details.is_add && details.child == this && GetWidget())
     NotifyAccessibilityEvent(ui::AX_EVENT_ALERT, true);
 }
 
 }  // namespace views