Move LayerImpl's bounds_delta to property trees

cc/layers/layer_impl.h

 // Copyright 2011 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_IMPL_H_
 #define CC_LAYERS_LAYER_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 251 matching lines @@
 
   // The client should be responsible for setting bounds, content bounds and
   // contents scale to appropriate values. LayerImpl doesn't calculate any of
   // them from the other values.
 
   void SetBounds(const gfx::Size& bounds);
   gfx::Size bounds() const;
   // Like bounds() but doesn't snap to int. Lossy on giant pages (e.g. millions
   // of pixels) due to use of single precision float.
   gfx::SizeF BoundsForScrolling() const;
-  void SetBoundsDelta(const gfx::Vector2dF& bounds_delta);
-  gfx::Vector2dF bounds_delta() const { return bounds_delta_; }
+  void SetViewportBoundsDelta(const gfx::Vector2dF& bounds_delta);
+  gfx::Vector2dF ViewportBoundsDelta() const;

[wkorman, 2017/04/25 18:38:05]

Document what this does in brief? In particular, re: the case where it could
return empty value, is that expected, when would it happen lifecycle-wise.

 
   void SetCurrentScrollOffset(const gfx::ScrollOffset& scroll_offset);
   gfx::ScrollOffset CurrentScrollOffset() const;
 
   gfx::ScrollOffset MaxScrollOffset() const;
   gfx::ScrollOffset ClampScrollOffsetToLimits(gfx::ScrollOffset offset) const;
   gfx::Vector2dF ClampScrollToMaxScrollOffset();
 
   // Returns the delta of the scroll that was outside of the bounds of the
   // initial scroll
@@ skipping 180 matching lines @@
 
   void ValidateQuadResourcesInternal(DrawQuad* quad) const;
 
   virtual const char* LayerTypeAsString() const;
 
   int layer_id_;
   LayerTreeImpl* layer_tree_impl_;
 
   std::unique_ptr<LayerImplTestProperties> test_properties_;
 
-  gfx::Vector2dF bounds_delta_;
-
   // Properties synchronized from the associated Layer.
   gfx::Size bounds_;
   int scroll_clip_layer_id_;
 
   gfx::Vector2dF offset_to_transform_parent_;
   uint32_t main_thread_scrolling_reasons_;
 
   bool user_scrollable_horizontal_ : 1;
   bool user_scrollable_vertical_ : 1;
   bool should_flatten_transform_from_property_tree_ : 1;
@@ skipping 67 matching lines @@
   // the overlay scrollbars. It's set on the scroll layer (not the scrollbar
   // layers) and consumed by LayerTreeImpl::PushPropertiesTo during activation.
   bool needs_show_scrollbars_ : 1;
 
   DISALLOW_COPY_AND_ASSIGN(LayerImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_LAYER_IMPL_H_