Do null check when setting ScrollClipLayer

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/debug/trace_event_impl.h"
 #include "base/lazy_instance.h"
 #include "base/strings/string_util.h"
@@ skipping 240 matching lines @@
 
 blink::WebPoint WebLayerImpl::scrollPosition() const {
   return gfx::PointAtOffsetFromOrigin(layer_->scroll_offset());
 }
 
 WebSize WebLayerImpl::maxScrollPosition() const {
   return layer_->MaxScrollOffset();
 }
 
 void WebLayerImpl::setScrollClipLayer(WebLayer* clip_layer) {
-  cc::Layer* cc_clip_layer =
-      clip_layer ? static_cast<WebLayerImpl*>(clip_layer)->layer() : 0;
-  layer_->SetScrollClipLayerId(cc_clip_layer->id());
+  if (!clip_layer) {
+    layer_->SetScrollClipLayerId(Layer::INVALID_ID);
+    return;
+  }
+  layer_->SetScrollClipLayerId(clip_layer->id());
 }
 
 bool WebLayerImpl::scrollable() const { return layer_->scrollable(); }
 
 void WebLayerImpl::setUserScrollable(bool horizontal, bool vertical) {
   layer_->SetUserScrollable(horizontal, vertical);
 }
 
 bool WebLayerImpl::userScrollableHorizontal() const {
   return layer_->user_scrollable_horizontal();
@@ skipping 162 matching lines @@
 void WebLayerImpl::setClipParent(blink::WebLayer* parent) {
   cc::Layer* clip_parent = NULL;
   if (parent)
     clip_parent = static_cast<WebLayerImpl*>(parent)->layer();
   layer_->SetClipParent(clip_parent);
 }
 
 Layer* WebLayerImpl::layer() const { return layer_.get(); }
 
 }  // namespace webkit