Track the currently scrolling ScrollNode instead of the scrolling layer

cc/trees/tree_synchronizer_unittest.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/trees/tree_synchronizer.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <set>
 #include <vector>
 
 #include "base/format_macros.h"
 #include "base/memory/ptr_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "cc/animation/animation_host.h"
 #include "cc/layers/layer.h"
 #include "cc/layers/layer_impl.h"
 #include "cc/test/animation_test_common.h"
 #include "cc/test/fake_impl_task_runner_provider.h"
 #include "cc/test/fake_layer_tree_host.h"
 #include "cc/test/fake_rendering_stats_instrumentation.h"
 #include "cc/test/stub_layer_tree_host_single_thread_client.h"
 #include "cc/test/test_task_graph_runner.h"
 #include "cc/trees/effect_node.h"
 #include "cc/trees/layer_tree_host_common.h"
+#include "cc/trees/scroll_node.h"
 #include "cc/trees/single_thread_proxy.h"
 #include "cc/trees/task_runner_provider.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace cc {
 namespace {
 
 bool AreScrollOffsetsEqual(const SyncedScrollOffset* a,
                            const SyncedScrollOffset* b) {
   return a->ActiveBase() == b->ActiveBase() &&
@@ skipping 459 matching lines @@
   scroll_layer->SetScrollClipLayerId(scroll_clip_layer->id());
   host_->SetRootLayer(layer_tree_root);
   host_->BuildPropertyTreesForTesting();
   host_->CommitAndCreatePendingTree();
   host_impl->ActivateSyncTree();
 
   ExpectTreesAreIdentical(layer_tree_root.get(),
                           host_impl->active_tree()->root_layer_for_testing(),
                           host_impl->active_tree());
 
-  host_impl->active_tree()->SetCurrentlyScrollingLayer(
-      host_impl->active_tree()->LayerById(scroll_layer->id()));
+  ScrollNode* scroll_node =
+      host_impl->active_tree()->property_trees()->scroll_tree.Node(
+          scroll_layer->scroll_tree_index());
+  host_impl->active_tree()->SetCurrentlyScrollingNode(scroll_node);
   transient_scroll_layer->SetScrollClipLayerId(Layer::INVALID_ID);
   host_->BuildPropertyTreesForTesting();
 
   host_impl->CreatePendingTree();
   host_->CommitAndCreatePendingTree();
   host_impl->ActivateSyncTree();
 
-  EXPECT_EQ(scroll_layer->id(),
-            host_impl->active_tree()->CurrentlyScrollingLayer()->id());
+  EXPECT_EQ(scroll_layer->scroll_tree_index(),
+            host_impl->active_tree()->CurrentlyScrollingNode()->id);
 }
 
 TEST_F(TreeSynchronizerTest, SynchronizeScrollTreeScrollOffsetMap) {
   host_->InitializeSingleThreaded(&single_thread_client_,
                                   base::ThreadTaskRunnerHandle::Get());
   LayerTreeSettings settings;
   FakeLayerTreeHostImplClient client;
   FakeImplTaskRunnerProvider task_runner_provider;
   FakeRenderingStatsInstrumentation stats_instrumentation;
   TestTaskGraphRunner task_graph_runner;
@@ skipping 62 matching lines @@
   std::unique_ptr<ScrollAndScaleSet> scroll_info(new ScrollAndScaleSet());
   scroll_tree.CollectScrollDeltas(scroll_info.get(), Layer::INVALID_ID);
   host_->proxy()->SetNeedsCommit();
   host_->ApplyScrollAndScale(scroll_info.get());
   EXPECT_EQ(gfx::ScrollOffset(20, 30), scroll_layer->scroll_offset());
   scroll_layer->SetScrollOffset(gfx::ScrollOffset(100, 100));
 
   // More update to ScrollOffset active delta: gfx::ScrollOffset(20, 20)
   scroll_tree.SetScrollOffset(scroll_layer_impl->id(),
                               gfx::ScrollOffset(40, 50));
-  host_impl->active_tree()->SetCurrentlyScrollingLayer(scroll_layer_impl);
+  host_impl->active_tree()->SetCurrentlyScrollingNode(
+      scroll_tree.Node(scroll_layer_impl->scroll_tree_index()));
 
   // Make one layer unscrollable so that scroll tree topology changes
   transient_scroll_layer->SetScrollClipLayerId(Layer::INVALID_ID);
   host_->BuildPropertyTreesForTesting();
 
   host_impl->CreatePendingTree();
   host_->CommitAndCreatePendingTree();
   host_impl->ActivateSyncTree();
 
-  EXPECT_EQ(scroll_layer->id(),
-            host_impl->active_tree()->CurrentlyScrollingLayer()->id());
+  EXPECT_EQ(scroll_layer->scroll_tree_index(),
+            host_impl->active_tree()->CurrentlyScrollingNode()->id);
   scroll_layer_offset->SetCurrent(gfx::ScrollOffset(20, 30));
   scroll_layer_offset->PullDeltaForMainThread();
   scroll_layer_offset->SetCurrent(gfx::ScrollOffset(40, 50));
   scroll_layer_offset->PushFromMainThread(gfx::ScrollOffset(100, 100));
   scroll_layer_offset->PushPendingToActive();
   EXPECT_TRUE(AreScrollOffsetsEqual(
       scroll_layer_offset.get(),
       host_impl->active_tree()
           ->property_trees()
           ->scroll_tree.GetSyncedScrollOffset(scroll_layer->id())));
@@ skipping 43 matching lines @@
   host_->CommitAndCreatePendingTree();
   host_impl->ActivateSyncTree();
   EXPECT_EQ(
       CombinedAnimationScale(0.f, 0.f),
       host_impl->active_tree()->property_trees()->GetAnimationScales(
           transform_layer->transform_tree_index(), host_impl->active_tree()));
 }
 
 }  // namespace
 }  // namespace cc