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

cc/trees/layer_tree_host_unittest_animation.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 <stdint.h>
 
 #include "cc/animation/animation_curve.h"
 #include "cc/animation/animation_host.h"
@@ skipping 807 matching lines @@
       host_impl->BlockNotifyReadyToActivateForTesting(false);
       return;
     }
 
     scoped_refptr<AnimationTimeline> timeline_impl =
         host_impl->animation_host()->GetTimelineById(timeline_id_);
     scoped_refptr<AnimationPlayer> player_impl =
         timeline_impl->GetPlayerById(player_child_id_);
 
     LayerImpl* scroll_layer_impl =
-        host_impl->active_tree()->root_layer()->children()[0];
+        host_impl->active_tree()->LayerById(scroll_layer_->id());
     Animation* animation = player_impl->element_animations()
                                ->GetAnimation(TargetProperty::SCROLL_OFFSET);
 
     if (!animation || animation->run_state() != Animation::RUNNING) {
       host_impl->BlockNotifyReadyToActivateForTesting(false);
       return;
     }
 
     // Block activation until the running animation has a chance to produce a
     // scroll delta.
     gfx::Vector2dF scroll_delta = ScrollDelta(scroll_layer_impl);
     if (scroll_delta.x() < 1.f || scroll_delta.y() < 1.f)
       return;
 
     host_impl->BlockNotifyReadyToActivateForTesting(false);
   }
 
   void WillActivateTreeOnThread(LayerTreeHostImpl* host_impl) override {
     if (host_impl->pending_tree()->source_frame_number() != 1)
       return;
     LayerImpl* scroll_layer_impl =
-        host_impl->pending_tree()->root_layer()->children()[0];
+        host_impl->pending_tree()->LayerById(scroll_layer_->id());
     EXPECT_EQ(final_postion_, scroll_layer_impl->CurrentScrollOffset());
   }
 
   void DidActivateTreeOnThread(LayerTreeHostImpl* host_impl) override {
     if (host_impl->active_tree()->source_frame_number() != 1)
       return;
     LayerImpl* scroll_layer_impl =
-        host_impl->active_tree()->root_layer()->children()[0];
+        host_impl->active_tree()->LayerById(scroll_layer_->id());
     EXPECT_EQ(final_postion_, scroll_layer_impl->CurrentScrollOffset());
     EndTest();
   }
 
   void AfterTest() override {
     EXPECT_EQ(final_postion_, scroll_layer_->scroll_offset());
   }
 
  private:
   FakeContentLayerClient client_;
@@ skipping 139 matching lines @@
     // After checking this on the sync tree, we will activate, which will cause
     // PrepareTiles to happen again (which races with the test exiting).
     if (TestEnded())
       return;
 
     scoped_refptr<AnimationTimeline> timeline_impl =
         host_impl->animation_host()->GetTimelineById(timeline_id_);
     scoped_refptr<AnimationPlayer> player_impl =
         timeline_impl->GetPlayerById(player_id_);
 
-    LayerImpl* root = host_impl->sync_tree()->root_layer();
-    LayerImpl* child = root->children()[0];
+    LayerImpl* child = host_impl->sync_tree()->LayerById(layer_->id());
     Animation* animation = player_impl->element_animations()->GetAnimation(
         TargetProperty::TRANSFORM);
 
     // The animation should be starting for the first frame.
     EXPECT_EQ(Animation::STARTING, animation->run_state());
 
     // And the transform should be propogated to the sync tree layer, at its
     // starting state which is 6,7.
     gfx::Transform expected_transform;
     expected_transform.Translate(6.0, 7.0);
@@ skipping 136 matching lines @@
     if (host_impl->active_tree()->source_frame_number() < 2)
       return;
     AnimationHost::AnimationControllerMap controllers_copy =
         host_impl->animation_host()->active_animation_controllers_for_testing();
     EXPECT_EQ(2u, controllers_copy.size());
     for (auto& it : controllers_copy) {
       int id = it.first;
       if (id == host_impl->RootLayer()->id()) {
         Animation* anim = it.second->GetAnimation(TargetProperty::TRANSFORM);
         EXPECT_GT((anim->start_time() - base::TimeTicks()).InSecondsF(), 0);
-      } else if (id == host_impl->RootLayer()->children()[0]->id()) {
+      } else if (id == layer_->id()) {
         Animation* anim = it.second->GetAnimation(TargetProperty::OPACITY);
         EXPECT_GT((anim->start_time() - base::TimeTicks()).InSecondsF(), 0);
       }
       EndTest();
     }
   }
 
   void AfterTest() override {}
 
  private:
@@ skipping 43 matching lines @@
         // animation still had its own transform node). But nodes can only get
         // added/deleted when something triggers a rebuild. Adding a layer
         // triggers a rebuild, and since the layer that had an animation before
         // no longer has one, it doesn't get a transform node in the rebuild.
         layer_->AddChild(Layer::Create());
         break;
     }
   }
 
   void DrawLayersOnThread(LayerTreeHostImpl* host_impl) override {
-    LayerImpl* root = host_impl->active_tree()->root_layer();
-    LayerImpl* child = root->children()[0];
+    LayerImpl* child = host_impl->active_tree()->LayerById(layer_->id());
     switch (host_impl->active_tree()->source_frame_number()) {
       case 0:
         // No animation yet.
         break;
       case 1:
         // Animation is started.
         EXPECT_TRUE(child->screen_space_transform_is_animating());
         break;
       case 2: {
         // The animation is removed, the transform that was set afterward is
@@ skipping 42 matching lines @@
         break;
       case 2:
         Animation* animation = player_->element_animations()->GetAnimation(
             TargetProperty::TRANSFORM);
         player_->RemoveAnimation(animation->id());
         break;
     }
   }
 
   void CommitCompleteOnThread(LayerTreeHostImpl* host_impl) override {
-    LayerImpl* root = host_impl->sync_tree()->root_layer();
-    LayerImpl* child = root->children()[0];
+    LayerImpl* child = host_impl->sync_tree()->LayerById(layer_->id());
     switch (host_impl->sync_tree()->source_frame_number()) {
       case 0:
         // No animation yet.
         break;
       case 1:
         // Animation is started.
         EXPECT_TRUE(child->screen_space_transform_is_animating());
         break;
       case 2:
         // The animation is removed/stopped.
         EXPECT_FALSE(child->screen_space_transform_is_animating());
         EndTest();
         break;
       default:
         NOTREACHED();
     }
   }
 
   void DrawLayersOnThread(LayerTreeHostImpl* host_impl) override {
-    LayerImpl* root = host_impl->active_tree()->root_layer();
-    LayerImpl* child = root->children()[0];
+    LayerImpl* child = host_impl->active_tree()->LayerById(layer_->id());
     switch (host_impl->active_tree()->source_frame_number()) {
       case 0:
         // No animation yet.
         break;
       case 1:
         // Animation is started.
         EXPECT_TRUE(child->screen_space_transform_is_animating());
         break;
       case 2:
         // The animation is removed/stopped.
@@ skipping 52 matching lines @@
   }
 
   void CommitCompleteOnThread(LayerTreeHostImpl* host_impl) override {
     switch (host_impl->sync_tree()->source_frame_number()) {
       case 1:
         PostSetNeedsCommitToMainThread();
         break;
       case 2:
         gfx::Transform expected_transform;
         expected_transform.Translate(5.f, 5.f);
-        LayerImpl* layer_impl =
-            host_impl->sync_tree()->root_layer()->children()[0];
+        LayerImpl* layer_impl = host_impl->sync_tree()->LayerById(layer_->id());
         EXPECT_EQ(expected_transform, layer_impl->DrawTransform());
         EndTest();
         break;
     }
   }
 
   void UpdateAnimationState(LayerTreeHostImpl* host_impl,
                             bool has_unfinished_animation) override {
     if (host_impl->active_tree()->source_frame_number() == 1 &&
         !has_unfinished_animation && !signalled_) {
@@ skipping 195 matching lines @@
  private:
   scoped_refptr<Layer> layer_;
   FakeContentLayerClient client_;
 };
 
 MULTI_THREAD_TEST_F(
     LayerTreeHostAnimationTestRebuildPropertyTreesOnAnimationSetNeedsCommit);
 
 }  // namespace
 }  // namespace cc