Cherry pick HarfBuzz white-space fix

third_party/harfbuzz-ng/src/hb-coretext.cc

 /*
  * Copyright © 2012,2013  Mozilla Foundation.
  * Copyright © 2012,2013  Google, Inc.
  *
  *  This is part of HarfBuzz, a text shaping library.
  *
  * Permission is hereby granted, without written agreement and without
  * license or royalty fees, to use, copy, modify, and distribute this
  * software and its documentation for any purpose, provided that the
  * above copyright notice and the following two paragraphs appear in
@@ skipping 770 matching lines @@
         FAIL ("CTTypesetterCreateLine failed");
     }
 
     CFArrayRef glyph_runs = CTLineGetGlyphRuns (line);
     unsigned int num_runs = CFArrayGetCount (glyph_runs);
     DEBUG_MSG (CORETEXT, NULL, "Num runs: %d", num_runs);
 
     buffer->len = 0;
     uint32_t status_and = ~0, status_or = 0;
     double advances_so_far = 0;
+    /* For right-to-left runs, CoreText returns the glyphs positioned such that
+     * any trailing whitespace is to the left of (0,0).  Adjust coordinate system
+     * to fix for that.  Test with any RTL string with trailing spaces.
+     * https://code.google.com/p/chromium/issues/detail?id=476913
+     */
+    if (HB_DIRECTION_IS_BACKWARD (buffer->props.direction))
+    {
+      advances_so_far -= CTLineGetTrailingWhitespaceWidth (line);
+      if (HB_DIRECTION_IS_VERTICAL (buffer->props.direction))
+          advances_so_far = -advances_so_far;
+    }
 
     const CFRange range_all = CFRangeMake (0, 0);
 
     for (unsigned int i = 0; i < num_runs; i++)
     {
       CTRunRef run = static_cast<CTRunRef>(CFArrayGetValueAtIndex (glyph_runs, i));
       CTRunStatus run_status = CTRunGetStatus (run);
       status_or  |= run_status;
       status_and &= run_status;
       DEBUG_MSG (CORETEXT, run, "CTRunStatus: %x", run_status);
@@ skipping 384 matching lines @@
 
 hb_bool_t
 _hb_coretext_aat_shape (hb_shape_plan_t    *shape_plan,
                         hb_font_t          *font,
                         hb_buffer_t        *buffer,
                         const hb_feature_t *features,
                         unsigned int        num_features)
 {
   return _hb_coretext_shape (shape_plan, font, buffer, features, num_features);
 }