DocumentLoader::InitialScrollState::was_scrolled_by_user is set in a bunch of different places and conditions.

Its purpose is to disable subsequent history scroll restore operations if the user scrolls while the frame is still loading.

I think it is supposed to be set for any user scroll (from main or cc) of any scroller in the document (not just the document itself).

When I looked at it for http://crrev.com/1273623006 it was called from WebViewImpl::ApplyViewportDeltas for compositor-thread viewport scrolls, and from EventHandler::setFrameWasScrolledByUser which despite the misleading name was invoked for PLSA overflow-scrolls.

In http://crrev.com/2144303002 the call site in WebViewImpl::ApplyViewportDeltas got moved into FrameView which I guess broke WebFrameTest.CompositorScrollIsUserScrollLongPage with RLS.  We're cargo-culting it into PLSA in http://crrev.com/c/526798 but we should probably:

- Set it in LFV::UpdateScrollOffset and PLSA::UpdateScrollOffset for kUserScroll || kCompositorScroll, for any scroller in any frame.

- Get rid of all the other places that are setting it like ScrollManager and Element::NativeApplyScroll.  I suspect those are leftovers from when we did not have reliable plumbing of ScrollType into UpdateScrollOffset (or whatever it was called at the time).