(WIP) Paint invalidation for slimming paint v2

Source/core/paint/PaintPhase.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 20 matching lines @@
 /*
  *  The painting of a layer occurs in three distinct phases.  Each phase involves
  *  a recursive descent into the layer's layout objects. The first phase is the background phase.
  *  The backgrounds and borders of all blocks are painted.  Inlines are not painted at all.
  *  Floats must paint above block backgrounds but entirely below inline content that can overlap them.
  *  In the foreground phase, all inlines are fully painted.  Inline replaced elements will get all
  *  three phases invoked on them during this phase.
  */
 
 enum PaintPhase {
+    PaintPhaseInvalidation = -1,
     PaintPhaseBlockBackground = 0,
     PaintPhaseChildBlockBackground = 1,
     PaintPhaseChildBlockBackgrounds = 2,
     PaintPhaseFloat = 3,
     PaintPhaseForeground = 4,
     PaintPhaseOutline = 5,
     PaintPhaseChildOutlines = 6,
     PaintPhaseSelfOutline = 7,
     PaintPhaseSelection = 8,
     PaintPhaseCollapsedTableBorders = 9,
     PaintPhaseTextClip = 10,
     PaintPhaseMask = 11,
     PaintPhaseClippingMask = 12,
     PaintPhaseMax = PaintPhaseClippingMask,
-    // These values must be kept in sync with DisplayItem::Type and DisplayItem::typeAsDebugString().
+    // These values except PaintPhaseInvalidation must be kept in sync with
+    // DisplayItem::Type and DisplayItem::typeAsDebugString().
 };
 
 // Those flags are meant as global tree operations. This means
 // that they should be constant for a paint phase.
 enum GlobalPaintFlag {
     GlobalPaintNormalPhase = 0,
     // Used when painting selection as part of a drag-image. This
     // flag disables a lot of the painting code and specifically
     // triggers a PaintPhaseSelection.
     GlobalPaintSelectionOnly = 1 << 0,
     // Used when painting a drag-image or printing in order to
     // ignore the hardware layers and paint the whole tree
     // into the topmost layer.
     GlobalPaintFlattenCompositingLayers = 1 << 1,
     // Used when printing in order to adapt the output to the medium, for
     // instance by not painting shadows and selections on text, and add
     // URL metadata for links.
     GlobalPaintPrinting = 1 << 2
 };
 
 typedef unsigned GlobalPaintFlags;
 
 } // namespace blink
 
 #endif // PaintPhase_h