Use a layer transform for the waiting throbber

ui/gfx/paint_throbber.h

 // Copyright (c) 2015 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.
 
 #ifndef UI_GFX_PAINT_THROBBER_H_
 #define UI_GFX_PAINT_THROBBER_H_
 
 #include "base/basictypes.h"
 #include "base/time/time.h"
 #include "third_party/skia/include/core/SkColor.h"
@@ skipping 10 matching lines @@
 struct GFX_EXPORT ThrobberWaitingState {
   // The amount of time that was spent in the waiting state.
   base::TimeDelta elapsed_time;
   // The color of the arc in the waiting state.
   SkColor color;
   // An opaque value used to cache calculations made by
   // PaintThrobberSpinningAfterWaiting.
   base::TimeDelta arc_time_offset;
 };
 
+GFX_EXPORT void PaintThrobberArc(Canvas* canvas,
+                                 const Rect& bounds,
+                                 SkColor color,
+                                 SkScalar start_angle,
+                                 SkScalar sweep);
+
 // Paints a single frame of the throbber in the "spinning", aka Material, state.
 GFX_EXPORT void PaintThrobberSpinning(Canvas* canvas,
     const Rect& bounds, SkColor color, const base::TimeDelta& elapsed_time);
 
 // Paints a throbber in the "waiting" state. Used when waiting on a network
 // response, for example.
 GFX_EXPORT void PaintThrobberWaiting(Canvas* canvas,
     const Rect& bounds, SkColor color, const base::TimeDelta& elapsed_time);
 
 // Paint a throbber in the "spinning" state, smoothly transitioning from a
@@ skipping 12 matching lines @@
     Canvas* canvas,
     const Rect& bounds,
     SkColor color,
     uint32_t frame,
     SkColor waiting_color,
     uint32_t final_waiting_frame);
 
 }  // namespace gfx
 
 #endif  // UI_GFX_PAINT_THROBBER_H_