Use private helpers in LayerImpl to shorten property tree references.

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 528 matching lines @@
   friend class TreeSynchronizer;
 
   // Layers that share a sorting context id will be sorted together in 3d
   // space.  0 is a special value that means this layer will not be sorted and
   // will be drawn in paint order.
   int sorting_context_id_;
 
   DrawMode current_draw_mode_;
 
  private:
+  PropertyTrees* GetPropertyTrees() const;

[wkorman, 2017/01/06 03:41:02]

I named these as GetXxx() since not-infrequently one would otherwise have an
issue with masking for example:

PropertyTrees* property_trees = property_trees();
// subsequently multiple refs to property_trees the variable

will require revision to use this->property_trees() on the RHS.

Also it's my understanding the lowercase-underscore names are only intended for
trivial getters and in this case we're doing some non-trivial dereferencing.

LayerImpl::GetElementTypeForAnimation() is a recent example that follows this
naming style.

Counterpoints are LayerImpl::ScrollOffsetForAnimation() and
LayerImpl::CurrentScrollOffset() which are camel case but don't have Get prefix.

YMMV. News at 11? Vote now!

[wkorman, 2017/01/06 17:37:32]

On reflection I'd like to rename these to remove the Get prefix but keep the
camel-case. That seems more common. Does this sound ok?

[danakj, 2017/01/06 17:50:06]

That will collide with the type name - and functions should be verbs and Get
prefix is the standard way to write that for accessors that are not hacker_case
(unless you're proposing that then ignore me).

+  EffectTree& GetEffectTree() const;
+  ScrollTree& GetScrollTree() const;
+  TransformTree& GetTransformTree() const;
+
   ElementId element_id_;
   uint32_t mutable_properties_;
   // Rect indicating what was repainted/updated during update.
   // Note that plugin layers bypass this and leave it empty.
   // This is in the layer's space.
   gfx::Rect update_rect_;
 
   // Denotes an area that is damaged and needs redraw. This is in the layer's
   // space.
   gfx::Rect damage_rect_;
@@ skipping 17 matching lines @@
   bool has_will_change_transform_hint_ : 1;
   bool needs_push_properties_ : 1;
   bool scrollbars_hidden_ : 1;
 
   DISALLOW_COPY_AND_ASSIGN(LayerImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_LAYER_IMPL_H_