MacViews: Style BUTTON_STYLE buttons using the "modern" UI

ui/views/controls/button/custom_button.h

Index: ui/views/controls/button/custom_button.h
diff --git a/ui/views/controls/button/custom_button.h b/ui/views/controls/button/custom_button.h
index d91d3e68771cd9ec6ec873891541b048ec1437a2..c478b9f1dd730d873e4106e0578f22095aa5fff6 100644
--- a/ui/views/controls/button/custom_button.h
+++ b/ui/views/controls/button/custom_button.h
@@ -16,6 +16,7 @@
 namespace views {
 
 class InkDropDelegate;
+class LabelButton;
 
 // A button with custom rendering. The base of ImageButton and LabelButton.
 // Note that this type of button is not focusable by default and will not be
@@ -34,6 +35,8 @@ class VIEWS_EXPORT CustomButton : public Button, public gfx::AnimationDelegate {
 
   static const CustomButton* AsCustomButton(const views::View* view);
   static CustomButton* AsCustomButton(views::View* view);
+  static const LabelButton* AsLabelButton(const views::View* view);

[sky, 2016/04/07 17:16:31]

I am not a fan of using the view class name for RTTI. It's brittle. Is there
another way to accomplish what you need that doesn't involve using the class
name?

[tapted, 2016/04/08 08:35:33]

There's not really any logic that depends on the RTTI - it's more just to be
defensive. So I've removed it in the latest CL. Currently this means that code
needs to be "careful" only to put the result of
PlatformStyle::CreateLabelButtonBorder onto a LabelButton.

We could make this agreement more formal by storing a LabelButton* data member
on LabelButtonBorder and ignoring (or DCHECKing) the |view| passed in via
Border::Paint into DialogButtonBorderMac

+  static LabelButton* AsLabelButton(views::View* view);
 
   ~CustomButton() override;