Allow unsetting scroll client

webkit/renderer/compositor_bindings/web_layer_impl.cc

Index: webkit/renderer/compositor_bindings/web_layer_impl.cc
diff --git a/webkit/renderer/compositor_bindings/web_layer_impl.cc b/webkit/renderer/compositor_bindings/web_layer_impl.cc
index 4f3a3b8a93e5666641c4f458aff90459f31f37a8..4969077605d862dec49127fc7684750e36b25e19 100644
--- a/webkit/renderer/compositor_bindings/web_layer_impl.cc
+++ b/webkit/renderer/compositor_bindings/web_layer_impl.cc
@@ -351,9 +351,13 @@ WebKit::WebLayerPositionConstraint WebLayerImpl::positionConstraint() const {
 
 void WebLayerImpl::setScrollClient(
     WebKit::WebLayerScrollClient* scroll_client) {
-  layer_->set_did_scroll_callback(
-      base::Bind(&WebKit::WebLayerScrollClient::didScroll,
-                 base::Unretained(scroll_client)));
+  if (scroll_client) {
+    layer_->set_did_scroll_callback(
+        base::Bind(&WebKit::WebLayerScrollClient::didScroll,
+                   base::Unretained(scroll_client)));
+  } else {
+    layer_->set_did_scroll_callback(base::Closure());
+  }
 }
 
 bool WebLayerImpl::isOrphan() const { return !layer_->layer_tree_host(); }