cc: Add a resource_provider_ dcheck in resource_pool creation.

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index 26c14925bf1d19c1c4f6e64d88e540e346f1f5ed..ad7b96f200b37b68ea73a2084b6f7bad2c51081c 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -2091,6 +2091,9 @@ void LayerTreeHostImpl::CreateResourceAndTileTaskWorkerPool(
     scoped_ptr<ResourcePool>* resource_pool,
     scoped_ptr<ResourcePool>* staging_resource_pool) {
   DCHECK(GetTaskRunner());
+  // TODO(vmpstr): Make this a DCHECK (or remove) when crbug.com/419086 is
+  // resolved.
+  CHECK(resource_provider_);
 
   // Pass the single-threaded synchronous task graph runner to the worker pool
   // if we're in synchronous single-threaded mode.