cc: Restructure access to LayerTreeHost in LayerTreeTests.

cc/trees/layer_tree_host_unittest_animation.cc

Index: cc/trees/layer_tree_host_unittest_animation.cc
diff --git a/cc/trees/layer_tree_host_unittest_animation.cc b/cc/trees/layer_tree_host_unittest_animation.cc
index 0b3f1b3297e7e1108d020efcef3abad0eeb597ab..44f7d83f7b6a7de0247a7305f6225bcd8156f957 100644
--- a/cc/trees/layer_tree_host_unittest_animation.cc
+++ b/cc/trees/layer_tree_host_unittest_animation.cc
@@ -742,8 +742,7 @@ class LayerTreeHostAnimationTestScrollOffsetChangesArePropagated
         std::unique_ptr<Animation> animation(Animation::Create(
             std::move(curve), 1, 0, TargetProperty::SCROLL_OFFSET));
         animation->set_needs_synchronized_start_time(true);
-        bool impl_scrolling_supported =
-            layer_tree_host()->proxy()->SupportsImplScrolling();
+        bool impl_scrolling_supported = proxy()->SupportsImplScrolling();
         if (impl_scrolling_supported)
           player_child_->AddAnimation(std::move(animation));
         else
@@ -1658,8 +1657,9 @@ class LayerTreeHostAnimationTestNotifyAnimationFinished
                               TargetProperty::Type target_property,
                               int group) override {
     called_animation_started_ = true;
-    layer_tree_host()->AnimateLayers(base::TimeTicks::FromInternalValue(
-        std::numeric_limits<int64_t>::max()));
+    layer_tree_host_in_process()->AnimateLayers(
+        base::TimeTicks::FromInternalValue(
+            std::numeric_limits<int64_t>::max()));
     PostSetNeedsCommitToMainThread();
   }