cc: Remove LayerImpl::children() calls from descendants of LayerTreeTest

cc/trees/layer_tree_host_unittest_context.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 <stdint.h>
 
 #include "base/memory/ptr_util.h"
 #include "cc/layers/heads_up_display_layer.h"
 #include "cc/layers/layer_impl.h"
@@ skipping 628 matching lines @@
   void InvalidateAndSetNeedsCommit() override {
     // Invalidate the render surface so we don't try to use a cached copy of the
     // surface.  We want to make sure to test the drawing paths for drawing to
     // a child surface.
     layer_->SetNeedsDisplay();
     LayerTreeHostContextTestLostContextSucceeds::InvalidateAndSetNeedsCommit();
   }
 
   void DrawLayersOnThread(LayerTreeHostImpl* host_impl) override {
     FakePictureLayerImpl* picture_impl = static_cast<FakePictureLayerImpl*>(
-        host_impl->active_tree()->root_layer()->children()[0]);
+        host_impl->active_tree()->LayerById(layer_->id()));
     EXPECT_TRUE(picture_impl->HighResTiling()
                     ->TileAt(0, 0)
                     ->draw_info()
                     .IsReadyToDraw());
   }
 
  protected:
   FakeContentLayerClient client_;
   scoped_refptr<Layer> root_;
   scoped_refptr<Layer> layer_;
@@ skipping 189 matching lines @@
 
   void DidActivateTreeOnThread(LayerTreeHostImpl* host_impl) override {
     LayerTreeHostContextTest::DidActivateTreeOnThread(host_impl);
 
     FakePictureLayerImpl* root_picture = NULL;
     FakePictureLayerImpl* child_picture = NULL;
     FakePictureLayerImpl* grandchild_picture = NULL;
 
     root_picture = static_cast<FakePictureLayerImpl*>(
         host_impl->active_tree()->root_layer());
-    child_picture =
-        static_cast<FakePictureLayerImpl*>(root_picture->children()[0]);
-    grandchild_picture =
-        static_cast<FakePictureLayerImpl*>(child_picture->children()[0]);
+    child_picture = static_cast<FakePictureLayerImpl*>(
+        host_impl->active_tree()->LayerById(child_->id()));
+    grandchild_picture = static_cast<FakePictureLayerImpl*>(
+        host_impl->active_tree()->LayerById(grandchild_->id()));
 
     ++num_commits_;
     switch (num_commits_) {
       case 1:
         EXPECT_EQ(0u, root_picture->release_resources_count());
         EXPECT_EQ(0u, child_picture->release_resources_count());
         EXPECT_EQ(0u, grandchild_picture->release_resources_count());
 
         // Lose the context and struggle to recreate it.
         LoseContext();
@@ skipping 730 matching lines @@
   void AfterTest() override {}
 
   bool deferred_;
 };
 
 SINGLE_AND_MULTI_THREAD_TEST_F(
     LayerTreeHostContextTestLoseAfterSendingBeginMainFrame);
 
 }  // namespace
 }  // namespace cc