ui: Cleanup class/struct forward declarations

cc/layers/nine_patch_layer_unittest.cc

Index: cc/layers/nine_patch_layer_unittest.cc
diff --git a/cc/layers/nine_patch_layer_unittest.cc b/cc/layers/nine_patch_layer_unittest.cc
index c85857011d6d31ec5dd430d6b2a7f3af2da47de0..440b608f9df12d6914685d70bb29111c5381f668 100644
--- a/cc/layers/nine_patch_layer_unittest.cc
+++ b/cc/layers/nine_patch_layer_unittest.cc
@@ -4,6 +4,7 @@
 
 #include "cc/layers/nine_patch_layer.h"
 
+#include "cc/animation/animation_host.h"
 #include "cc/resources/resource_provider.h"
 #include "cc/resources/scoped_ui_resource.h"
 #include "cc/test/fake_layer_tree_host.h"
@@ -29,8 +30,9 @@ namespace {
 class NinePatchLayerTest : public testing::Test {
  protected:
   void SetUp() override {
-    layer_tree_host_ =
-        FakeLayerTreeHost::Create(&fake_client_, &task_graph_runner_);
+    animation_host_ = AnimationHost::CreateForTesting(ThreadInstance::MAIN);
+    layer_tree_host_ = FakeLayerTreeHost::Create(
+        &fake_client_, &task_graph_runner_, animation_host_.get());
   }
 
   void TearDown() override {
@@ -39,6 +41,7 @@ class NinePatchLayerTest : public testing::Test {
 
   FakeLayerTreeHostClient fake_client_;
   TestTaskGraphRunner task_graph_runner_;
+  std::unique_ptr<AnimationHost> animation_host_;
   std::unique_ptr<FakeLayerTreeHost> layer_tree_host_;
 };