Introduce some util code for drawing vector assets.

ui/views/controls/throbber.h

Index: ui/views/controls/throbber.h
diff --git a/ui/views/controls/throbber.h b/ui/views/controls/throbber.h
index c5bed816a584b40fdf0dcea4c9324589c3faf963..43288158b8c8bbe611a04eadd4af792ee4801f90 100644
--- a/ui/views/controls/throbber.h
+++ b/ui/views/controls/throbber.h
@@ -11,10 +11,6 @@
 #include "base/timer/timer.h"
 #include "ui/views/view.h"
 
-namespace gfx {
-class ImageSkia;
-}
-
 namespace views {
 
 // Throbbers display an animation, usually used as a status indicator.
@@ -46,9 +42,6 @@ class VIEWS_EXPORT Throbber : public View {
   // Whether or not we should display a checkmark.
   bool checked_;
 
-  // The checkmark image. Will be null until it's used (if ever).
-  const gfx::ImageSkia* checkmark_;
-
   DISALLOW_COPY_AND_ASSIGN(Throbber);
 };