Use private helpers in LayerImpl to shorten property tree references.

cc/layers/layer_impl.h

Index: cc/layers/layer_impl.h
diff --git a/cc/layers/layer_impl.h b/cc/layers/layer_impl.h
index c0ec013171c81f46f2274bdb513928c071a80b55..e0fa9cf92e37827318f77ad7e24ccc49882d5d17 100644
--- a/cc/layers/layer_impl.h
+++ b/cc/layers/layer_impl.h
@@ -546,6 +546,11 @@ class CC_EXPORT LayerImpl {
   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.