Make LayerTreeImpl::SetCurrentlyScrollingNode use element ids over layer ids

cc/trees/layer_tree_host_unittest_scroll.cc

 // Copyright 2012 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/layer_tree_host.h"
 
 #include "base/location.h"
 #include "base/memory/ptr_util.h"
 #include "base/memory/weak_ptr.h"
 #include "base/single_thread_task_runner.h"
@@ skipping 552 matching lines @@
         scroll_amount_(2, -1),
         num_scrolls_(0) {}
 
   void SetupTree() override {
     layer_tree_host()->SetDeviceScaleFactor(device_scale_factor_);
 
     scoped_refptr<Layer> root_layer = Layer::Create();
     root_layer->SetBounds(gfx::Size(10, 10));
 
     root_scroll_layer_ = FakePictureLayer::Create(&fake_content_layer_client_);
+    root_scroll_layer_->SetElementId(
+        LayerIdToElementIdForTesting(root_scroll_layer_->id()));
     root_scroll_layer_->SetBounds(gfx::Size(110, 110));
     root_scroll_layer_->SetPosition(gfx::PointF());
     root_scroll_layer_->SetIsDrawable(true);
 
     CreateVirtualViewportLayers(root_layer.get(), root_scroll_layer_,
                                 root_layer->bounds(), root_layer->bounds(),
                                 layer_tree_host());
 
     child_layer_ = FakePictureLayer::Create(&fake_content_layer_client_);
     child_layer_->set_did_scroll_callback(
         base::Bind(&LayerTreeHostScrollTestCaseWithChild::DidScroll,
                    base::Unretained(this)));
+    child_layer_->SetElementId(
+        LayerIdToElementIdForTesting(child_layer_->id()));
     child_layer_->SetBounds(gfx::Size(110, 110));
 
     if (scroll_child_layer_) {
       // Scrolls on the child layer will happen at 5, 5. If they are treated
       // like device pixels, and device scale factor is 2, then they will
       // be considered at 2.5, 2.5 in logical pixels, and will miss this layer.
       child_layer_->SetPosition(gfx::PointF(5.f, 5.f));
     } else {
       // Adjust the child layer horizontally so that scrolls will never hit it.
       child_layer_->SetPosition(gfx::PointF(60.f, 5.f));
     }
 
     scoped_refptr<Layer> outer_container_layer =
         layer_tree_host()->outer_viewport_scroll_layer()->parent();
 
     child_layer_->SetIsDrawable(true);
     child_layer_->SetScrollClipLayerId(outer_container_layer->id());
+    child_layer_->SetElementId(
+        LayerIdToElementIdForTesting(child_layer_->id()));
     child_layer_->SetBounds(root_scroll_layer_->bounds());
     root_scroll_layer_->AddChild(child_layer_);
 
     if (scroll_child_layer_) {
       expected_scroll_layer_ = child_layer_;
       expected_no_scroll_layer_ = root_scroll_layer_;
     } else {
       expected_scroll_layer_ = root_scroll_layer_;
       expected_no_scroll_layer_ = child_layer_;
     }
@@ skipping 816 matching lines @@
     Layer* layer_;
   };
 
   Layer* CreateScrollLayer(Layer* parent, FakeLayerScrollClient* client) {
     scoped_refptr<PictureLayer> scroll_layer =
         PictureLayer::Create(&fake_content_layer_client_);
     scroll_layer->SetBounds(gfx::Size(110, 110));
     scroll_layer->SetPosition(gfx::PointF());
     scroll_layer->SetIsDrawable(true);
     scroll_layer->SetScrollClipLayerId(parent->id());
+    scroll_layer->SetElementId(
+        LayerIdToElementIdForTesting(scroll_layer->id()));
     scroll_layer->SetBounds(gfx::Size(parent->bounds().width() + 100,
                                       parent->bounds().height() + 100));
     scroll_layer->set_did_scroll_callback(base::Bind(
         &FakeLayerScrollClient::DidScroll, base::Unretained(client)));
     client->owner_ = this;
     client->layer_ = scroll_layer.get();
     parent->AddChild(scroll_layer);
     return scroll_layer.get();
   }
 
@@ skipping 798 matching lines @@
   CompletionEvent* impl_side_invalidation_event_ = nullptr;
 
   // Main thread.
   int num_of_deltas_ = 0;
 };
 
 MULTI_THREAD_TEST_F(MAYBE_LayerTreeHostScrollTestImplSideInvalidation);
 
 }  // namespace
 }  // namespace cc