cc: Single-threaded impl-side painting for unit tests

cc/test/layer_tree_test.cc

Index: cc/test/layer_tree_test.cc
diff --git a/cc/test/layer_tree_test.cc b/cc/test/layer_tree_test.cc
index 2681b434a8df9f4e7c3923a48dd3d7afb20f8c8d..ea047271c2c27809340aa3bf61a0cc5454daf7be 100644
--- a/cc/test/layer_tree_test.cc
+++ b/cc/test/layer_tree_test.cc
@@ -627,11 +627,7 @@ void LayerTreeTest::RunTest(bool threaded,
   // Spend less time waiting for BeginFrame because the output is
   // mocked out.
   settings_.refresh_rate = 200.0;
-  if (impl_side_painting) {
-    DCHECK(threaded)
-        << "Don't run single thread + impl side painting, it doesn't exist.";
-    settings_.impl_side_painting = true;
-  }
+  settings_.impl_side_painting = impl_side_painting;
   InitializeSettings(&settings_);
 
   main_task_runner_->PostTask(