Add RenderObject::needsResizeLayout

Source/core/rendering/RenderBox.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2006, 2007 Apple 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
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 512 matching lines @@
         LayoutRectRecorder recorder(*this);
         LayoutUnit oldWidth = width();
         updateLogicalWidth();
         // If we shrink to fit our width may have changed, so we still need full layout.
         if (oldWidth != width())
             return false;
         updateLogicalHeight();
         return true;
     }
 
+    bool tryLayoutDoingResizeOnly()
+    {
+        // FIXME: For now this is for RenderView only. Needs more verifications before applied to generic objects.
+        ASSERT(isRenderView());
+        // For now what needed to do happens to be the same as tryLayoutDoingPositionedMovementOnly() does.
+        return tryLayoutDoingPositionedMovementOnly();

[Julien - ping for review, 2014/03/21 19:39:10]

I don't think this is fundamentally right to do a positioned movement only.
RenderView is artificially positioned (it's more of an implementation detail)
but it doesn't *move*, it resizes and that's different. Also this won't handle
the following cases:
- vh units.
- positioned objects with a percentage bottom / top.

[Xianzhu, 2014/03/21 20:10:36]

Actually the intent is not to do a position movement. Calling it just because
the things to do happen to be the same: update logical width and height; if
logical width is different, returns false.

To avoid confusion, I can also repeat the code here.
In these cases, before RenderView's tryLayoutDoingResizeOnly() is called, the
objects have been setNeedsLayout() (which also marked the ancestors
setNeedsLayout()). This will cause a normal full layout (after early returning
from trySimplifiedLayout), despite the setNeedsSizeLayout() flag.

The unit test in https://codereview.chromium.org/204813002/ covers these cases.

This is why we need setNeedsResizeLayout(): otherwise during layout we can't
know if the object needs a simple resize, or a full layout triggered by its
descendants.

+    }
+
     LayoutRect maskClipRect();
 
     virtual PositionWithAffinity positionForPoint(const LayoutPoint&) OVERRIDE;
 
     void removeFloatingOrPositionedChildFromBlockLists();
 
     RenderLayer* enclosingFloatPaintingLayer() const;
 
     virtual int firstLineBoxBaseline() const { return -1; }
     virtual int inlineBlockBaseline(LineDirectionMode) const { return -1; } // Returns -1 if we should skip this box when computing the baseline of an inline-block.
@@ skipping 235 matching lines @@
         if (UNLIKELY(inlineBoxWrapper() != 0))
             deleteLineBoxWrapper();
     }
 
     ensureRareData().m_inlineBoxWrapper = boxWrapper;
 }
 
 } // namespace WebCore
 
 #endif // RenderBox_h