Only update remote frame viewport intersection when paint is clean.

The viewport intersection shouldn't be updated for a force layout or
other non-BeginMainFrame lifecycle update.

BUG=842368
R=kenrb@chromium.org

Change-Id: Ifd656b495e60e8b1413df8126c7b6ff95933abaf
Reviewed-on: https://chromium-review.googlesource.com/1056491Reviewed-by: Ken Buchanan <kenrb@chromium.org>
Commit-Queue: Stefan Zager <szager@chromium.org>
Cr-Commit-Position: refs/heads/master@{#558133}

third_party/blink/renderer/core/frame/remote_frame_view.cc

@@ -67,6 +67,8 @@ void RemoteFrameView::UpdateViewportIntersectionsForSubtree(
     DocumentLifecycle::LifecycleState target_state) {
   if (!remote_frame_->OwnerLayoutObject())
     return;
+  if (target_state < DocumentLifecycle::kPaintClean)
+    return;
 
   LocalFrameView* local_root_view =
       ToLocalFrame(remote_frame_->Tree().Parent())->LocalFrameRoot().View();