cc: Change tile manager perftest to use layers.

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 b51d6f9cbc3c1aa95a4f3ef58ef2b4c5586a3e1c..af12c38c8b65356eaca20a7569dac4e3769a195c 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -1140,6 +1140,18 @@ void LayerTreeHostImpl::DidInitializeVisibleTileForTesting() {
   DidInitializeVisibleTile();
 }
 
+void LayerTreeHostImpl::ResetTreesForTesting() {
+  if (active_tree_)
+    active_tree_->DetachLayerTree();
+  active_tree_ = LayerTreeImpl::create(this);
+  if (pending_tree_)
+    pending_tree_->DetachLayerTree();
+  pending_tree_.reset();
+  if (recycle_tree_)
+    recycle_tree_->DetachLayerTree();
+  recycle_tree_.reset();
+}
+
 void LayerTreeHostImpl::EnforceManagedMemoryPolicy(
     const ManagedMemoryPolicy& policy) {