cc: Add some more infrastructure for two trees

cc/layer_tree_impl.cc

Index: cc/layer_tree_impl.cc
diff --git a/cc/layer_tree_impl.cc b/cc/layer_tree_impl.cc
index a113316c77b3dc79bac020ad0c65d8b3af0df422..8cc941eaee04870d1fa54839737e6c70415ff30f 100644
--- a/cc/layer_tree_impl.cc
+++ b/cc/layer_tree_impl.cc
@@ -106,6 +106,28 @@ FrameRateCounter* LayerTreeImpl::frame_rate_counter() const {
   return layer_tree_host_impl_->fpsCounter();
 }
 
+bool LayerTreeImpl::IsActiveTree() const {
+  return layer_tree_host_impl_->activeTree() == this;
+}
+
+bool LayerTreeImpl::IsPendingTree() const {
+  return layer_tree_host_impl_->pendingTree() == this;
+}
+
+LayerImpl* LayerTreeImpl::ActiveTreeLayerById(int id) {
+  LayerTreeImpl* tree = layer_tree_host_impl_->activeTree();
+  if (!tree)
+    return NULL;
+  return tree->LayerById(id);
+}
+
+LayerImpl* LayerTreeImpl::PendingTreeLayerById(int id) {
+  LayerTreeImpl* tree = layer_tree_host_impl_->pendingTree();
+  if (!tree)
+    return NULL;
+  return tree->LayerById(id);
+}
+
 void LayerTreeImpl::SetNeedsRedraw() {
   layer_tree_host_impl_->setNeedsRedraw();
 }