Add a function to scroll a platform canvas. This uses the platform scroll...

gfx/blit.h

 // Copyright (c) 2009 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 GFX_BLIT_H_
 #define GFX_BLIT_H_
 
 #include "gfx/native_widget_types.h"
 #include "gfx/point.h"
 #include "gfx/rect.h"
@@ skipping 24 matching lines @@
                          const Rect& dst_rect,
                          skia::PlatformCanvas *src_canvas,
                          const Point& src_origin);
 
 // Blits a rectangle from the source canvas into the destination canvas.
 void BlitCanvasToCanvas(skia::PlatformCanvas *dst_canvas,
                         const Rect& dst_rect,
                         skia::PlatformCanvas *src_canvas,
                         const Point& src_origin);
 
+// Scrolls the given subset of the given canvas by the given amount.
+// The canvas should not have a clip or a transform applied, since platforms
+// may implement those operations differently.
+void ScrollCanvas(skia::PlatformCanvas* canvas,
+                  const Rect& clip,
+                  const Point& amount);
+
 }  // namespace gfx
 
 #endif  // GFX_BLIT_H_