Re-enable Scroll Anchor Serialization

Now that root layer scrolling and scroll anchoring are on unconditionally,
it no longer makes sense to check FrameView's ShouldPerformScrollAnchoring.
This inadvertently turned ScrollAnchorSerialization off even when the flag
was turned on.

Change-Id: I56f5224bb2aef6d06e4d0086b76a6122d4ac4ad3
Reviewed-on: https://chromium-review.googlesource.com/1100068Reviewed-by: Steve Kobes <skobes@chromium.org>
Commit-Queue: Patrick Noland <pnoland@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567149}

third_party/blink/renderer/core/loader/frame_loader.cc

@@ -257,9 +257,7 @@ void FrameLoader::SetDefersLoading(bool defers) {
 }
 
 bool FrameLoader::ShouldSerializeScrollAnchor() {
-  return frame_ && frame_->View() &&
-         RuntimeEnabledFeatures::ScrollAnchorSerializationEnabled() &&
-         frame_->View()->ShouldPerformScrollAnchoring();
+  return RuntimeEnabledFeatures::ScrollAnchorSerializationEnabled();
 }
 
 void FrameLoader::SaveScrollAnchor() {