CC Animations: Enable external animation host for blink.

content/test/web_layer_tree_view_impl_for_testing.cc

Index: content/test/web_layer_tree_view_impl_for_testing.cc
diff --git a/content/test/web_layer_tree_view_impl_for_testing.cc b/content/test/web_layer_tree_view_impl_for_testing.cc
index a70aa245306638f9dfa4cc9c089f5a415844edea..0bb14af220a9e902d95dc6e268bce5e356201128 100644
--- a/content/test/web_layer_tree_view_impl_for_testing.cc
+++ b/content/test/web_layer_tree_view_impl_for_testing.cc
@@ -22,6 +22,7 @@
 #include "third_party/WebKit/public/platform/WebLayer.h"
 #include "third_party/WebKit/public/platform/WebLayerTreeView.h"
 #include "third_party/WebKit/public/platform/WebSize.h"
+#include "third_party/WebKit/public/web/WebRuntimeFeatures.h"
 
 using blink::WebColor;
 using blink::WebRect;
@@ -42,6 +43,9 @@ void WebLayerTreeViewImplForTesting::Initialize() {
 
   // Accelerated animations are enabled for unit tests.
   settings.accelerated_animation_enabled = true;
+  // External cc::AnimationHost is enabled for unit tests.
+  settings.use_compositor_animation_timelines = true;
+
   cc::LayerTreeHost::InitParams params;
   params.client = this;
   params.settings = &settings;