[LayoutNG] Misc fixes in ShapingLineBreaker

third_party/WebKit/Source/platform/fonts/shaping/HarfBuzzShaper.cpp

 /*
  * Copyright (c) 2012 Google Inc. All rights reserved.
  * Copyright (C) 2013 BlackBerry Limited. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 695 matching lines @@
   range_data.start = start;
   range_data.end = end;
   SetFontFeatures(font, &range_data.font_features);
 
   while (run_segmenter.Consume(&segment_range)) {
     // Only shape segments overlapping with the range indicated by start and
     // end. Not only those strictly within.
     if (start < segment_range.end && end > segment_range.start)
       ShapeSegment(&range_data, segment_range, result.Get());
   }
+  DCHECK(!result->NumCharacters() || (start == result->StartIndexForResult() &&
+                                      end == result->EndIndexForResult()));
   return result.Release();
 }
 
 PassRefPtr<ShapeResult> HarfBuzzShaper::Shape(const Font* font,
                                               TextDirection direction) const {
   return Shape(font, direction, 0, text_length_);
 }
 
 }  // namespace blink