Do null check when setting ScrollClipLayer

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 5f76315980eb98305a8c5429cce4edaba7c28a89..a0caaf53a49e9baf86dbdfb506a6ec12808a9234 100644
--- a/webkit/renderer/compositor_bindings/web_layer_impl.cc
+++ b/webkit/renderer/compositor_bindings/web_layer_impl.cc
@@ -258,9 +258,11 @@ WebSize WebLayerImpl::maxScrollPosition() const {
 }
 
 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(); }