Find root scroll layer at tree activation

cc/top_controls_manager_unittest.cc

 // Copyright 2013 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/top_controls_manager.h"
 
 #include "base/memory/scoped_ptr.h"
 #include "base/time.h"
 #include "cc/layer_impl.h"
 #include "cc/layer_tree_impl.h"
 #include "cc/test/fake_impl_proxy.h"
 #include "cc/test/fake_layer_tree_host_impl.h"
 #include "cc/top_controls_manager_client.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/gfx/vector2d_f.h"
 
 namespace cc {
 namespace {
 
 static const float kTopControlsHeight = 100;
 
 class MockTopControlsManagerClient : public TopControlsManagerClient {
  public:
   MockTopControlsManagerClient()
       : host_impl_(&proxy_),
         redraw_needed_(false),
         update_draw_properties_needed_(false) {
     active_tree_ = LayerTreeImpl::create(&host_impl_);
     root_scroll_layer_ = LayerImpl::create(active_tree_.get(), 1);
-    active_tree_->set_root_scroll_layer(root_scroll_layer_.get());
   }
 
   virtual ~MockTopControlsManagerClient() {}
 
   virtual void setNeedsRedraw() OVERRIDE {
     redraw_needed_ = true;
   }
 
   virtual void setNeedsUpdateDrawProperties() OVERRIDE {
     update_draw_properties_needed_ = true;
   }
 
-  virtual LayerTreeImpl* activeTree() OVERRIDE {
-    return active_tree_.get();
+  virtual bool haveRootScrollLayer() const OVERRIDE {
+    return true;
+  }
+
+  virtual float rootScrollLayerTotalScrollY() const OVERRIDE {
+    return root_scroll_layer_->scrollOffset().y() +
+           root_scroll_layer_->scrollDelta().y();
+  }
+
+  LayerImpl* rootScrollLayer() {
+    return root_scroll_layer_.get();
   }
 
   TopControlsManager* manager() {
     if (!manager_)
       manager_ = TopControlsManager::Create(this, kTopControlsHeight);
     return manager_.get();
   }
 
-  LayerImpl* rootScrollLayer() {
-    return root_scroll_layer_.get();
-  }
-
  private:
   FakeImplProxy proxy_;
   FakeLayerTreeHostImpl host_impl_;
   scoped_ptr<LayerTreeImpl> active_tree_;
   scoped_ptr<LayerImpl> root_scroll_layer_;
   scoped_ptr<TopControlsManager> manager_;
   bool redraw_needed_;
   bool update_draw_properties_needed_;
 };
 
@@ skipping 127 matching lines @@
     previous_offset = manager->controls_top_offset();
   }
   EXPECT_FALSE(manager->animation());
   EXPECT_EQ(0.f, manager->controls_top_offset());
   EXPECT_EQ(0.f, manager->content_top_offset());
   EXPECT_TRUE(manager->is_overlay_mode());
 }
 
 }  // namespace
 }  // namespace cc