Allow unsetting scroll client

webkit/renderer/compositor_bindings/web_layer_impl.cc

 // 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.
 
 #include "webkit/renderer/compositor_bindings/web_layer_impl.h"
 
 #include "base/bind.h"
 #include "base/strings/string_util.h"
 #include "cc/animation/animation.h"
 #include "cc/base/region.h"
@@ skipping 333 matching lines @@
     const WebKit::WebLayerPositionConstraint& constraint) {
   layer_->SetPositionConstraint(ToLayerPositionConstraint(constraint));
 }
 
 WebKit::WebLayerPositionConstraint WebLayerImpl::positionConstraint() const {
   return ToWebLayerPositionConstraint(layer_->position_constraint());
 }
 
 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(); }
 
 Layer* WebLayerImpl::layer() const { return layer_.get(); }
 
 }  // namespace webkit