cc : Add DCHECKs to ensure we have valid proprety tree indices at commit

cc/layers/scrollbar_layer_unittest.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 <stddef.h>
 
 #include <unordered_map>
 
 #include "base/memory/ptr_util.h"
 #include "base/threading/thread_task_runner_handle.h"
@@ skipping 367 matching lines @@
   root_layer->SetScrollOffset(gfx::ScrollOffset(0, 0));
   scrollbar_layer->SetBounds(gfx::Size(70, 10));
   scrollbar_layer->SetScrollElementId(root_layer->element_id());
   scrollbar_layer->fake_scrollbar()->set_location(gfx::Point(20, 10));
   scrollbar_layer->fake_scrollbar()->set_track_rect(gfx::Rect(30, 10, 50, 10));
   scrollbar_layer->fake_scrollbar()->set_thumb_thickness(10);
   scrollbar_layer->fake_scrollbar()->set_thumb_length(4);
   LayerImpl* root_clip_layer_impl = nullptr;
   PaintedScrollbarLayerImpl* scrollbar_layer_impl = nullptr;
 
+  layer_tree_host_->BuildPropertyTreesForTesting();
   UPDATE_AND_EXTRACT_LAYER_POINTERS();
   EXPECT_EQ(gfx::Rect(10, 0, 4, 10).ToString(),
             scrollbar_layer_impl->ComputeThumbQuadRect().ToString());
 
   scrollbar_layer->fake_scrollbar()->set_has_thumb(false);
 
   UPDATE_AND_EXTRACT_LAYER_POINTERS();
   EXPECT_EQ(gfx::Rect(10, 0, 0, 0).ToString(),
             scrollbar_layer_impl->ComputeThumbQuadRect().ToString());
 }
@@ skipping 339 matching lines @@
       scrollbar->Orientation(), kThumbThickness, kTrackStart,
       kIsLeftSideVerticalScrollbar, scroll_layer->element_id());
   scroll_layer->AddChild(child1);
   scroll_layer->InsertChild(scrollbar_layer, 1);
   layer_tree_root->AddChild(scroll_layer);
   layer_tree_host_->SetRootLayer(layer_tree_root);
 
   layer_tree_root->SetBounds(gfx::Size(2, 2));
   scroll_layer->SetBounds(gfx::Size(10, 10));
   layer_tree_host_->UpdateLayers();
-  layer_tree_host_->CommitAndCreateLayerImplTree();
   LayerTreeHostImpl* host_impl = layer_tree_host_->host_impl();
+  host_impl->CreatePendingTree();
+  layer_tree_host_->CommitAndCreatePendingTree();
+  host_impl->ActivateSyncTree();
   EXPECT_TRUE(host_impl->ScrollbarAnimationControllerForElementId(
       scroll_layer->element_id()));
 
   scroll_layer->SetBounds(gfx::Size(20, 20));
   scroll_layer->SetForceRenderSurfaceForTesting(true);
   layer_tree_host_->UpdateLayers();
   host_impl->CreatePendingTree();
   layer_tree_host_->CommitAndCreatePendingTree();
   host_impl->ActivateSyncTree();
   EffectNode* node =
@@ skipping 517 matching lines @@
   TestScale(gfx::Rect(1240, 0, 15, 1333), 2.7754839f);
   TestScale(gfx::Rect(1240, 0, 15, 677), 2.46677136f);
 
   // Horizontal Scrollbars.
   TestScale(gfx::Rect(0, 1240, 1333, 15), 2.7754839f);
   TestScale(gfx::Rect(0, 1240, 677, 15), 2.46677136f);
 }
 
 }  // namespace
 }  // namespace cc