RenderTextHarfBuzz: Fix glyph offset calculation

ui/gfx/render_text_harfbuzz.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/gfx/render_text_harfbuzz.h"
 
 #include <map>
 
 #include "base/debug/leak_annotations.h"
 #include "base/i18n/bidi_line_iterator.h"
@@ skipping 249 matching lines @@
 
   FaceCache* face_cache = &face_caches[skia_face->uniqueID()];
   if (face_cache->first == 0) {
     // These HarfBuzz faces live indefinitely and are intentionally leaked.
     ANNOTATE_SCOPED_MEMORY_LEAK;
     hb_face_t* harfbuzz_face = CreateHarfBuzzFace(skia_face);
     *face_cache = FaceCache(harfbuzz_face, GlyphCache());
   }
 
   hb_font_t* harfbuzz_font = hb_font_create(face_cache->first);
-  // TODO(ckocagil): Investigate whether disabling hinting here has any effect
-  // on text quality.
-  int upem = hb_face_get_upem(face_cache->first);
-  hb_font_set_scale(harfbuzz_font, upem, upem);
+
+  const int scale = SkScalarToFixed(text_size);
+  hb_font_set_scale(harfbuzz_font, scale, scale);
   FontData* hb_font_data = new FontData(&face_cache->second);
   hb_font_data->paint_.setTypeface(skia_face);
   hb_font_data->paint_.setTextSize(text_size);
   hb_font_set_funcs(harfbuzz_font, g_font_funcs.Get().get(), hb_font_data,
                     DeleteByType<FontData>);
   hb_font_make_immutable(harfbuzz_font);
   return harfbuzz_font;
 }
 
 // Returns true if characters of |block_code| may trigger font fallback.
@@ skipping 709 matching lines @@
   run->glyphs.reset(new uint16[run->glyph_count]);
   run->glyph_to_char.reset(new uint32[run->glyph_count]);
   run->positions.reset(new SkPoint[run->glyph_count]);
   for (size_t i = 0; i < run->glyph_count; ++i) {
     run->glyphs[i] = infos[i].codepoint;
     run->glyph_to_char[i] = infos[i].cluster;
     const int x_offset =
         SkScalarRoundToInt(SkFixedToScalar(hb_positions[i].x_offset));
     const int y_offset =
         SkScalarRoundToInt(SkFixedToScalar(hb_positions[i].y_offset));
-    run->positions[i].set(run->width + x_offset, y_offset);
+    run->positions[i].set(run->width + x_offset, -y_offset);
     run->width +=
         SkScalarRoundToInt(SkFixedToScalar(hb_positions[i].x_advance));
   }
 
   hb_buffer_destroy(buffer);
   hb_font_destroy(harfbuzz_font);
 }
 
 }  // namespace gfx