Disentangle updating the ScrollingCoordinator from RenderLayerCompositor

Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 2814 matching lines @@
 
 void FrameView::updateLayoutAndStyleForPainting()
 {
     // Updating layout can run script, which can tear down the FrameView.
     RefPtr<FrameView> protector(this);
 
     updateLayoutAndStyleIfNeededRecursive();
 
     if (RenderView* view = renderView()) {
         InspectorInstrumentation::willUpdateLayerTree(view->frame());
+
         view->compositor()->updateIfNeededRecursive();
+
+        // FIXME: Is it really possible to be inCompositingMode and not have a ScrollingCoordinator?

[ojan, 2014/06/12 03:49:57]

I tried removing the inCompositingMode check once and tests did fail. If you can
remove it and tests don't fail, then I think we're OK. FWIW, this is one of the
few cases where the inCompositingMode bit is actually not stale. Nearly
everywhere else we read it we have no guarantee that it's not stale. I think we
need to change nearly every caller of this function and the
staleInCompositingMode function to do something else.

+        // FIXME: Is it really possible to have a RenderView and not have a Page?

[ojan, 2014/06/12 03:49:57]

I don't think so. This code is littered with impossible defensive code. I've
removed a bunch of such things.

[ojan, 2014/06/12 03:49:57]

I don't think so. This code is littered with impossible defensive code. I've
removed a bunch of such things.

+        if (view->compositor()->inCompositingMode() && m_frame->isMainFrame() && m_frame->page() && m_frame->page()->scrollingCoordinator())
+            m_frame->page()->scrollingCoordinator()->updateAfterCompositingChangeIfNeeded();
+
         InspectorInstrumentation::didUpdateLayerTree(view->frame());
     }
 
     scrollContentsIfNeededRecursive();
 }
 
 void FrameView::updateLayoutAndStyleIfNeededRecursive()
 {
     // We have to crawl our entire tree looking for any FrameViews that need
     // layout and make sure they are up to date.
@@ skipping 427 matching lines @@
 void FrameView::willRemoveScrollbar(Scrollbar* scrollbar, ScrollbarOrientation orientation)
 {
     ScrollableArea::willRemoveScrollbar(scrollbar, orientation);
     if (AXObjectCache* cache = axObjectCache()) {
         cache->remove(scrollbar);
         cache->handleScrollbarUpdate(this);
     }
 }
 
 } // namespace WebCore