ASSERTION FAILED: !m_overflow

third_party/WebKit/Source/core/layout/line/InlineBox.h

 /*
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2009, 2010, 2011 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.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 333 matching lines @@
         void setBidiEmbeddingLevel(unsigned char bidiEmbeddingLevel) { m_bidiEmbeddingLevel = bidiEmbeddingLevel; }
 
         ADD_BOOLEAN_BITFIELD(dirty, Dirty);
         ADD_BOOLEAN_BITFIELD(extracted, Extracted);
         ADD_BOOLEAN_BITFIELD(hasVirtualLogicalHeight, HasVirtualLogicalHeight);
         ADD_BOOLEAN_BITFIELD(isHorizontal, IsHorizontal);
         // for RootInlineBox
         ADD_BOOLEAN_BITFIELD(endsWithBreak, EndsWithBreak); // Whether the line ends with a <br>.
         // shared between RootInlineBox and InlineTextBox
         ADD_BOOLEAN_BITFIELD(hasSelectedChildrenOrCanHaveLeadingExpansion, HasSelectedChildrenOrCanHaveLeadingExpansion);
+
+        // This boolean tracks whether we know this box to have no overflow.

[leviw_travelin_and_unemployed, 2015/11/10 20:23:22]

"whether we know this box has no overflow"

[Julien - ping for review, 2015/11/10 23:52:47]

Changed.

+        //
+        // Note that this boolean shouldn't be set if we could have overflow.

[leviw_travelin_and_unemployed, 2015/11/10 20:23:22]

I don't feel that the middle 2 lines of this comment are useful.

[Julien - ping for review, 2015/11/10 23:52:47]

I strongly think they are (or at least something similar). When looking at the
boolean's lifecycle, it downed on me that it's never reset if it's ever cleared.
Those lines are meant to clarify this: it's a _conservative_ estimation and we
do allow some type of errors.

[leviw_travelin_and_unemployed, 2015/11/12 22:57:51]

Can you explain to me how "tracks whether we know this box has no overflow" and
that it "shouldn't be set if we could have overflow" add different information?

[Julien - ping for review, 2015/11/13 00:31:32]

Fair point, amended the comment to avoid this duplication:

// This boolean will never be set if there is potential for overflow,
// but it will be eagerly cleared in the opposite case. As such, it's
// a conservative tracking of the absence of overflow.

+        // As such, it's a conservative tracking of the absence of overflow.
+        //
+        // For whether we have overflow, callers should use m_overflow on
+        // InlineFlowBox.
         ADD_BOOLEAN_BITFIELD(knownToHaveNoOverflow, KnownToHaveNoOverflow);
         ADD_BOOLEAN_BITFIELD(hasEllipsisBoxOrHyphen, HasEllipsisBoxOrHyphen);
         // for InlineTextBox
         ADD_BOOLEAN_BITFIELD(dirOverride, DirOverride);
         ADD_BOOLEAN_BITFIELD(isText, IsText); // Whether or not this object represents text with a non-zero height. Includes non-image list markers, text boxes.
 
     private:
         mutable unsigned m_determinedIfNextOnLineExists : 1;
 
     public:
@@ skipping 79 matching lines @@
 
 } // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showTree(const blink::InlineBox*);
 void showLineTree(const blink::InlineBox*);
 #endif
 
 #endif // InlineBox_h