Implement interest rects for synchronized paint.

third_party/WebKit/Source/core/layout/LayoutScrollbar.cpp

 /*
  * Copyright (C) 2008, 2009 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 21 matching lines @@
 #include "core/layout/LayoutPart.h"
 #include "core/layout/LayoutScrollbarPart.h"
 #include "core/layout/LayoutScrollbarTheme.h"
 #include "core/layout/LayoutView.h"
 #include "platform/graphics/GraphicsContext.h"
 
 namespace blink {
 
 PassRefPtrWillBeRawPtr<Scrollbar> LayoutScrollbar::createCustomScrollbar(ScrollableArea* scrollableArea, ScrollbarOrientation orientation, Node* ownerNode, LocalFrame* owningFrame)
 {
+    fprintf(stderr, "custom scrollbar\n");

[ajuma, 2015/10/09 22:03:55]

Leftover from debugging? :)

[chrishtr, 2015/10/09 22:28:19]

Oops, fixed.

     return adoptRefWillBeNoop(new LayoutScrollbar(scrollableArea, orientation, ownerNode, owningFrame));
 }
 
 LayoutScrollbar::LayoutScrollbar(ScrollableArea* scrollableArea, ScrollbarOrientation orientation, Node* ownerNode, LocalFrame* owningFrame)
     : Scrollbar(scrollableArea, orientation, RegularScrollbar, LayoutScrollbarTheme::layoutScrollbarTheme())
     , m_owner(ownerNode)
     , m_owningFrame(owningFrame)
 {
     ASSERT(ownerNode || owningFrame);
 
@@ skipping 315 matching lines @@
     Scrollbar::invalidateRect(rect);
 
     // FIXME: invalidate only the changed part.
     if (LayoutBox* owningLayoutObject = this->owningLayoutObject()) {
         for (auto& part : m_parts)
             owningLayoutObject->invalidateDisplayItemClientForNonCompositingDescendantsOf(*part.value);
     }
 }
 
 }