Harden a security CHECK in Font::individualCharacterRanges

third_party/WebKit/Source/platform/fonts/Font.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2006, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (c) 2007, 2008, 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
@@ skipping 755 matching lines @@
 Vector<CharacterRange> Font::individualCharacterRanges(const TextRun& run) const
 {
     // TODO(pdr): Android is temporarily (crbug.com/577306) using the old simple
     // shaper and using the complex shaper here can show differences between
     // the two shapers. This function is currently only called through SVG
     // which now exclusively uses the complex shaper, so the primary difference
     // will be improved shaping in SVG when compared to HTML.
     FontCachePurgePreventer purgePreventer;
     CachingWordShaper shaper(m_fontFallbackList->shapeCache(m_fontDescription));
     auto ranges = shaper.individualCharacterRanges(this, run);
-    DCHECK_EQ(ranges.size(), run.length());
+    // The shaper should return ranges.size == run.length but on some platforms
+    // (OSX10.9.5) we are seeing cases in the upper end of the unicode range
+    // where this is not true (see: crbug.com/620952). To catch these cases on
+    // more popular platforms, and to protect users, we are using a CHECK here.
+    CHECK_EQ(ranges.size(), run.length());
     return ranges;
 }
 
 float Font::floatWidthForSimpleText(const TextRun& run, HashSet<const SimpleFontData*>* fallbackFonts, FloatRect* glyphBounds) const
 {
     SimpleShaper shaper(this, run, nullptr, fallbackFonts, glyphBounds);
     shaper.advance(run.length());
     return shaper.runWidthSoFar();
 }
 
@@ skipping 67 matching lines @@
 {
     return m_fontFallbackList && m_fontFallbackList->loadingCustomFonts();
 }
 
 bool Font::isFallbackValid() const
 {
     return !m_fontFallbackList || m_fontFallbackList->isValid();
 }
 
 } // namespace blink