cc : Calculate jitter without using layer hierarchy

cc/trees/layer_tree_host_impl_unittest.cc

Index: cc/trees/layer_tree_host_impl_unittest.cc
diff --git a/cc/trees/layer_tree_host_impl_unittest.cc b/cc/trees/layer_tree_host_impl_unittest.cc
index d81c3a8b4b790141b88935188548c5eff9792080..80dbed1c925af5f5b89c005659dd18956c33f4be 100644
--- a/cc/trees/layer_tree_host_impl_unittest.cc
+++ b/cc/trees/layer_tree_host_impl_unittest.cc
@@ -10349,9 +10349,11 @@ TEST_F(LayerTreeHostImplTest, JitterTest) {
     content_layer->SetTransform(translate);
 
     LayerTreeImpl* pending_tree = host_impl_->pending_tree();
+    LayerTreeImpl* active_tree = host_impl_->active_tree();
     pending_tree->PushPageScaleFromMainThread(1.f, 1.f, 1.f);
-    LayerImpl* last_scrolled_layer = pending_tree->LayerById(
-        host_impl_->active_tree()->LastScrolledLayerId());
+    ScrollNode* node = active_tree->property_trees()->scroll_tree.Node(
+        active_tree->LastScrolledScrollNodeId());
+    LayerImpl* last_scrolled_layer = pending_tree->LayerById(node->owner_id);
 
     // When building property trees from impl side, the builder uses the scroll
     // offset of layer_impl to initialize the scroll offset in scroll tree:
@@ -10374,8 +10376,7 @@ TEST_F(LayerTreeHostImplTest, JitterTest) {
 
     pending_tree->set_needs_update_draw_properties();
     pending_tree->UpdateDrawProperties(false);
-    float jitter =
-        LayerTreeHostCommon::CalculateFrameJitter(last_scrolled_layer);
+    float jitter = LayerTreeHostCommon::CalculateFrameJitter(content_layer);
     // There should not be any jitter measured till we hit the fixed point hits
     // threshold.
     float expected_jitter =