Revert of 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 eedbd3d2c90f05c17b6c34245853c369038d3de5..2681b434a8df9f4e7c3923a48dd3d7afb20f8c8d 100644
--- a/cc/test/layer_tree_test.cc
+++ b/cc/test/layer_tree_test.cc
@@ -202,9 +202,6 @@
   }
 
   virtual void BlockNotifyReadyToActivateForTesting(bool block) OVERRIDE {
-    CHECK(settings().impl_side_painting);
-    CHECK(proxy()->ImplThreadTaskRunner())
-        << "Not supported for single-threaded mode.";
     block_notify_ready_to_activate_for_testing_ = block;
     if (!block && notify_ready_to_activate_was_blocked_) {
       NotifyReadyToActivate();
@@ -630,7 +627,11 @@
   // Spend less time waiting for BeginFrame because the output is
   // mocked out.
   settings_.refresh_rate = 200.0;
-  settings_.impl_side_painting = impl_side_painting;
+  if (impl_side_painting) {
+    DCHECK(threaded)
+        << "Don't run single thread + impl side painting, it doesn't exist.";
+    settings_.impl_side_painting = true;
+  }
   InitializeSettings(&settings_);
 
   main_task_runner_->PostTask(