[LayoutNG] Initial letter-spacing and word-spacing support

third_party/WebKit/Source/platform/fonts/shaping/CachingWordShapeIterator.h

 /*
  * Copyright (C) 2015 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 29 matching lines @@
   STACK_ALLOCATED();
   WTF_MAKE_NONCOPYABLE(CachingWordShapeIterator);
 
  public:
   CachingWordShapeIterator(ShapeCache* cache,
                            const TextRun& run,
                            const Font* font)
       : shape_cache_(cache),
         text_run_(run),
         font_(font),
-        spacing_(run, font->GetFontDescription()),
+        spacing_(run),
         width_so_far_(0),
         start_index_(0) {
     DCHECK(font);
 
     // Shaping word by word is faster as each word is cached. If we cannot
     // use the cache or if the font doesn't support word by word shaping
     // fall back on shaping the entire run.
     shape_by_word_ = font_->CanShapeWordByWord();
+
+    if (!run.SpacingDisabled())

[ikilpatrick, 2017/06/29 16:17:59]

Can you add a comment here as to why spacing might be disabled, and what this
does?

+      spacing_.SetSpacingAndExpansion(font->GetFontDescription());
   }
 
   bool Next(RefPtr<const ShapeResult>* word_result) {
     if (UNLIKELY(text_run_.AllowTabs()))
       return NextForAllowTabs(word_result);
 
     if (!shape_by_word_) {
       if (start_index_)
         return false;
       *word_result = ShapeWord(text_run_, font_);
@@ skipping 126 matching lines @@
         return false;
     }
     DCHECK(*word_result);
     width_so_far_ += (*word_result)->Width();
     return true;
   }
 
   ShapeCache* shape_cache_;
   const TextRun& text_run_;
   const Font* font_;
-  ShapeResultSpacing spacing_;
+  ShapeResultSpacing<TextRun> spacing_;
   float width_so_far_;  // Used only when allowTabs()
   unsigned start_index_ : 31;
   unsigned shape_by_word_ : 1;
 };
 
 }  // namespace blink
 
 #endif  // CachingWordShapeIterator_h