Clean LayerImpl's scroll offset callers in unit tests.

cc/layers/layer.h

 // Copyright 2010 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 CC_LAYERS_LAYER_H_
 #define CC_LAYERS_LAYER_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 288 matching lines @@
     return touch_event_handler_region_;
   }
 
   void set_did_scroll_callback(const base::Closure& callback) {
     did_scroll_callback_ = callback;
   }
 
   void SetForceRenderSurface(bool force_render_surface);
   bool force_render_surface() const { return force_render_surface_; }
 
-  gfx::Vector2dF ScrollDelta() const { return gfx::Vector2dF(); }
   gfx::ScrollOffset CurrentScrollOffset() const { return scroll_offset_; }
 
   void SetDoubleSided(bool double_sided);
   bool double_sided() const { return double_sided_; }
 
   void SetShouldFlattenTransform(bool flatten);
   bool should_flatten_transform() const { return should_flatten_transform_; }
 
   bool Is3dSorted() const { return sorting_context_id_ != 0; }
 
@@ skipping 453 matching lines @@
 
   std::vector<FrameTimingRequest> frame_timing_requests_;
   bool frame_timing_requests_dirty_;
 
   DISALLOW_COPY_AND_ASSIGN(Layer);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_LAYER_H_