Plumb PinchVirtualViewport layers into CC.

content/renderer/gpu/render_widget_compositor.cc

Index: content/renderer/gpu/render_widget_compositor.cc
diff --git a/content/renderer/gpu/render_widget_compositor.cc b/content/renderer/gpu/render_widget_compositor.cc
index ec047de79e75121b1b95846b05ac1568eb7a7a72..29ca19e4c2c7a8dca5fc3ad1b0670ce4046e84ff 100644
--- a/content/renderer/gpu/render_widget_compositor.cc
+++ b/content/renderer/gpu/render_widget_compositor.cc
@@ -489,6 +489,26 @@ void RenderWidgetCompositor::registerForAnimations(WebKit::WebLayer* layer) {
       layer_tree_host_->animation_registrar());
 }
 
+void RenderWidgetCompositor::registerViewportLayers(
+    const WebKit::WebLayer* pageScaleLayer,
+    const WebKit::WebLayer* innerViewportScrollLayer,
+    const WebKit::WebLayer* outerViewportScrollLayer) {
+  layer_tree_host_->RegisterViewportLayers(
+      static_cast<const webkit::WebLayerImpl*>(pageScaleLayer)->layer(),
+      // The innerviewport layer will only exist when using pinch.

[enne (OOO), 2013/09/11 20:13:03]

I think it's the outer viewport layer that's optional and not the inner.  The
inner is affected by pinch, but the outer one is not.  So, I'd say the inner one
already exists.

[wjmaclean, 2013/09/12 18:16:47]

Yes, right. I keep forgetting we call the newly created layer "inner" so as not
to have to re-organize the existing layers, but conceptually it's the out
viewport layer that's optional.

+      innerViewportScrollLayer ? static_cast<const webkit::WebLayerImpl*>(
+                                     innerViewportScrollLayer)->layer()
+                               : 0,
+      static_cast<const webkit::WebLayerImpl*>(outerViewportScrollLayer)
+          ->layer());
+}
+
+void RenderWidgetCompositor::clearViewportLayers() {
+  layer_tree_host_->RegisterViewportLayers(scoped_refptr<cc::Layer>(),
+                                           scoped_refptr<cc::Layer>(),
+                                           scoped_refptr<cc::Layer>());
+}
+
 bool RenderWidgetCompositor::compositeAndReadback(
     void *pixels, const WebRect& rect_in_device_viewport) {
   return layer_tree_host_->CompositeAndReadback(pixels,