Turn on compositing for animations with software compositor.

content/browser/gpu/gpu_data_manager_impl_private.cc

Index: content/browser/gpu/gpu_data_manager_impl_private.cc
diff --git a/content/browser/gpu/gpu_data_manager_impl_private.cc b/content/browser/gpu/gpu_data_manager_impl_private.cc
index ae9f6bf1d1763afa51e1f597e1fdea841decc13b..c0113832411047efc49a79bc2b94ca6e21b5dd1d 100644
--- a/content/browser/gpu/gpu_data_manager_impl_private.cc
+++ b/content/browser/gpu/gpu_data_manager_impl_private.cc
@@ -795,6 +795,7 @@ void GpuDataManagerImplPrivate::UpdateRendererWebPrefs(
     prefs->force_compositing_mode = true;
     prefs->accelerated_compositing_enabled = true;
     prefs->accelerated_compositing_for_3d_transforms_enabled = true;
+    prefs->accelerated_compositing_for_animation_enabled = true;
     prefs->accelerated_compositing_for_plugins_enabled = true;
     prefs->accelerated_compositing_for_video_enabled = true;
   }