Add VectorIconButton functionality to ImageButton.

ui/views/controls/button/image_button.h

Index: ui/views/controls/button/image_button.h
diff --git a/ui/views/controls/button/image_button.h b/ui/views/controls/button/image_button.h
index eba2a835a40eff5f07a628558b2fe1fd5ad48b16..fc2a0d5edb67802d8a9fe07ef48ffa58b182578f 100644
--- a/ui/views/controls/button/image_button.h
+++ b/ui/views/controls/button/image_button.h
@@ -73,6 +73,8 @@ class VIEWS_EXPORT ImageButton : public CustomButton {
     draw_image_mirrored_ = mirrored;
   }
 
+  void SetPadding(const gfx::Insets& padding);

[sky, 2017/03/16 04:12:42]

SetPadding makes it sound like this is setting something in addition to the
border, which isn't the case. I would rather callers explicitly set the border.
Less confusion as what SetBorder(...) does and less duplicate ways of doing the
same thing.

+
   // Overridden from View:
   gfx::Size GetPreferredSize() const override;
   const char* GetClassName() const override;