BR styled clear is ignored while partially relayouting.

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 1527 matching lines @@
         // the replaced elements later. In partial layout mode, line boxes are not
         // deleted and only dirtied. In that case, we can layout the replaced
         // elements at the same time.
         Vector<LayoutBox*> replacedChildren;
         for (InlineWalker walker(this); !walker.atEnd(); walker.advance()) {
             LayoutObject* o = walker.current();
 
             if (!layoutState.hasInlineChild() && o->isInline())
                 layoutState.setHasInlineChild(true);
 
+            if (o->isBR() && o->style()->clear() != CNONE)
+                layoutState.setContainsBRWithClear(true);
+
             if (o->isReplaced() || o->isFloating() || o->isOutOfFlowPositioned()) {
                 LayoutBox* box = toLayoutBox(o);
 
                 updateBlockChildDirtyBitsBeforeLayout(relayoutChildren, *box);
 
                 if (o->isOutOfFlowPositioned()) {
                     o->containingBlock()->insertPositionedObject(box);
                 } else if (o->isFloating()) {
                     layoutState.floats().append(FloatWithRect(box));
                 } else if (isFullLayout || o->needsLayout()) {
@@ skipping 275 matching lines @@
     }
 
     return true;
 }
 
 bool LayoutBlockFlow::matchedEndLine(LineLayoutState& layoutState, const InlineBidiResolver& resolver, const InlineIterator& endLineStart, const BidiStatus& endLineStatus)
 {
     if (resolver.position() == endLineStart) {
         if (resolver.status() != endLineStatus)
             return false;
+
+        // A trailing BR can be collapsed as it usually doesn't contribute to the height,
+        // but if it has a clear style we need to force it to layout in the context of floats
+        // to honor that style.
+        if (layoutState.containsBRWithClear() && containsFloats())
+            return false;
         return checkPaginationAndFloatsAtEndLine(layoutState);
     }
 
     // The first clean line doesn't match, but we can check a handful of following lines to try
     // to match back up.
     static int numLines = 8; // The # of lines we're willing to match against.
     RootInlineBox* originalEndLine = layoutState.endLine();
     RootInlineBox* line = originalEndLine;
     for (int i = 0; i < numLines && line; i++, line = line->nextRootBox()) {
         if (line->lineBreakObj() == resolver.position().object() && line->lineBreakPos() == resolver.position().offset()) {
@@ skipping 180 matching lines @@
     float logicalLeft = logicalLeftOffsetForLine(logicalHeight(), false).toFloat();
     float availableLogicalWidth = logicalRightOffsetForLine(logicalHeight(), false) - logicalLeft;
     updateLogicalWidthForAlignment(textAlign, 0, 0, logicalLeft, totalLogicalWidth, availableLogicalWidth, 0);
 
     if (!style()->isLeftToRightDirection())
         return logicalWidth() - logicalLeft;
     return logicalLeft;
 }
 
 }