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

ui/views/window/dialog_delegate.cc

Index: ui/views/window/dialog_delegate.cc
diff --git a/ui/views/window/dialog_delegate.cc b/ui/views/window/dialog_delegate.cc
index 64759d95c3fb38e284f5ce976eff52c137bd8858..e6b179e538ae26e2f385864063a042d7d8560324 100644
--- a/ui/views/window/dialog_delegate.cc
+++ b/ui/views/window/dialog_delegate.cc
@@ -200,12 +200,7 @@ NonClientFrameView* DialogDelegate::CreateDialogFrameView(Widget* widget) {
       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);