Remove root layer specialness in calculateDrawTransforms

cc/test/layer_tree_test_common.cc

Index: cc/test/layer_tree_test_common.cc
diff --git a/cc/test/layer_tree_test_common.cc b/cc/test/layer_tree_test_common.cc
index 686cd278c3831faa61424868682bb3eba46e0da1..dc739d0bd58ca24a9337f04f502a8837d4fe0fa4 100644
--- a/cc/test/layer_tree_test_common.cc
+++ b/cc/test/layer_tree_test_common.cc
@@ -348,9 +348,9 @@ void ThreadedTest::postSetNeedsAnimateToMainThread()
     m_mainThreadProxy->postTask(createThreadTask(this, &ThreadedTest::dispatchSetNeedsAnimate));
 }
 
-void ThreadedTest::postAddAnimationToMainThread()
+void ThreadedTest::postAddAnimationToMainThread(Layer* layerToReceiveAnimation)
 {
-    m_mainThreadProxy->postTask(createThreadTask(this, &ThreadedTest::dispatchAddAnimation));
+    m_mainThreadProxy->postTask(createThreadTask(this, &ThreadedTest::dispatchAddAnimation, layerToReceiveAnimation));
 }
 
 void ThreadedTest::postAddInstantAnimationToMainThread()
@@ -454,15 +454,15 @@ void ThreadedTest::dispatchAddInstantAnimation()
         addOpacityTransitionToLayer(*m_layerTreeHost->rootLayer(), 0, 0, 0.5, false);
 }
 
-void ThreadedTest::dispatchAddAnimation()
+void ThreadedTest::dispatchAddAnimation(Layer* layerToReceiveAnimation)
 {
     DCHECK(Proxy::isMainThread());
 
     if (m_finished)
         return;
 
-    if (m_layerTreeHost.get() && m_layerTreeHost->rootLayer())
-        addOpacityTransitionToLayer(*m_layerTreeHost->rootLayer(), 10, 0, 0.5, true);
+    if (layerToReceiveAnimation)
+        addOpacityTransitionToLayer(*layerToReceiveAnimation, 10, 0, 0.5, true);
 }
 
 void ThreadedTest::dispatchSetNeedsAnimateAndCommit()