Avoid rogue line float re-layout.

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

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2003, 2004, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc.
  *               All right reserved.
  * Copyright (C) 2010 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
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 1914 matching lines @@
         LayoutBox* box = toLayoutBox(o);
         box->setMayNeedPaintInvalidation();
 
         updateBlockChildDirtyBitsBeforeLayout(relayoutChildren, *box);
 
         if (o->isOutOfFlowPositioned()) {
           o->containingBlock()->insertPositionedObject(box);
         } else if (o->isFloating()) {
           layoutState.floats().append(FloatWithRect(box));
           if (box->needsLayout()) {
-            box->layout();
-            // Dirty any lineboxes potentially affected by the float, but don't
-            // search outside this object as we are only interested in dirtying
-            // lineboxes to which we may attach the float.
+            // Be sure to at least mark the first line affected by the float as
+            // dirty, so that the float gets relaid out. Otherwise we'll miss
+            // it. After float layout, if it turns out that it changed size,
+            // any lines after this line will be deleted and relaid out.
             dirtyLinesFromChangedChild(box, MarkOnlyThis);
           }
         } else if (isFullLayout || o->needsLayout()) {
           // Atomic inline.
           box->dirtyLineBoxes(isFullLayout);
           o->layoutIfNeeded();
         }
       } else if (o->isText() ||
                  (o->isLayoutInline() && !walker.atEndOfInline())) {
         if (!o->isText())
@@ skipping 562 matching lines @@
 
 bool LayoutBlockFlow::paintedOutputOfObjectHasNoEffectRegardlessOfSize() const {
   // LayoutBlockFlow is in charge of paint invalidation of the first line.
   if (firstLineBox())
     return false;
 
   return LayoutBlock::paintedOutputOfObjectHasNoEffectRegardlessOfSize();
 }
 
 }  // namespace blink