Pinch/Zoom Infrastructure & Plumbing CL

cc/trees/layer_tree_host.h

Index: cc/trees/layer_tree_host.h
diff --git a/cc/trees/layer_tree_host.h b/cc/trees/layer_tree_host.h
index e66cd06cfcd770ecc1c672dfe01508b91099afa3..0a537c892d39ab735e0629d9a57ec3b5b5f57ed4 100644
--- a/cc/trees/layer_tree_host.h
+++ b/cc/trees/layer_tree_host.h
@@ -191,6 +191,12 @@ class CC_EXPORT LayerTreeHost {
       scoped_refptr<Layer> page_scale_layer,
       scoped_refptr<Layer> inner_viewport_scroll_layer,
       scoped_refptr<Layer> outer_viewport_scroll_layer);
+  Layer* inner_viewport_scroll_layer() const {
+    return inner_viewport_scroll_layer_.get();
+  }
+  Layer* outer_viewport_scroll_layer() const {
+    return outer_viewport_scroll_layer_.get();
+  }
 
   const LayerTreeSettings& settings() const { return settings_; }
 
@@ -231,6 +237,9 @@ class CC_EXPORT LayerTreeHost {
                                base::TimeDelta duration);
 
   void ApplyScrollAndScale(const ScrollAndScaleSet& info);
+  gfx::Vector2d DistributeScrollOffsetToViewports(const gfx::Vector2d offset,
+                                                  Layer* layer);
+  gfx::Vector2d BlinkScrollOffset(const Layer* layer) const;

[enne (OOO), 2014/01/02 19:28:17]

What does BlinkScrollOffset mean? What about TotalViewportScrollOffset?

Also, is this necessary? Scrolls go to Blink in two ways. 
LayerTreeHostClient::ApplyScrollAndScale sets the total scroll for the main
frame (which should include the viewports) and WebLayerScrollClient::didScroll
(the callback called via Layer::SetScrollOffsetFromImplSide) sets offsets per
layer for non-root (I think) layers (which shouldn't include viewports).

I'm trying to say that I think that WebLayerImpl should just ask the layer for
its scroll offset and that the total scroll offset should just get set via
ApplyScrollAndScale, and this function should only get called in that instance,
not in the WebLayerImpl::scrollPosition() function.

[wjmaclean, 2014/01/03 21:57:12]

This was code I experimented with to fix a failing unit test. It seems that
since I added it the test has either disappeared, or it's behaviour has been
accommodated by some other change I've made, since I can now remove this code
and the tests seem to run fine.

Removed.

 
   void SetImplTransform(const gfx::Transform& transform);