Create single thread synchronous task graph runner when necessary with gpu disabled.

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 0bf40594b49d519a242d450b1859190577331892..cccf917c5527213207072b770165f42b773f7bc3 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -2038,6 +2038,15 @@ void LayerTreeHostImpl::CreateResourceAndTileTaskWorkerPool(
                               : proxy_->MainThreadTaskRunner();
   DCHECK(task_runner);
 
+  // Pass the single-threaded synchronous task graph runner to the worker pool
+  // if we're in synchronous single-threaded mode.
+  TaskGraphRunner* task_graph_runner = task_graph_runner_;
+  if (IsSynchronousSingleThreaded()) {
+    DCHECK(!single_thread_synchronous_task_graph_runner_);
+    single_thread_synchronous_task_graph_runner_.reset(new TaskGraphRunner);
+    task_graph_runner = single_thread_synchronous_task_graph_runner_.get();
+  }
+
   ContextProvider* context_provider = output_surface_->context_provider();
   if (!context_provider) {
     *resource_pool =
@@ -2048,15 +2057,6 @@ void LayerTreeHostImpl::CreateResourceAndTileTaskWorkerPool(
     return;
   }
 
-  // Pass the single-threaded synchronous task graph runner to the worker pool
-  // if we're in synchronous single-threaded mode.
-  TaskGraphRunner* task_graph_runner = task_graph_runner_;
-  if (IsSynchronousSingleThreaded()) {
-    DCHECK(!single_thread_synchronous_task_graph_runner_);
-    single_thread_synchronous_task_graph_runner_.reset(new TaskGraphRunner);
-    task_graph_runner = single_thread_synchronous_task_graph_runner_.get();
-  }
-
   if (use_gpu_rasterization_) {
     *resource_pool =
         ResourcePool::Create(resource_provider_.get(), GL_TEXTURE_2D);