Make -webkit-font-kerning actually work.

Source/core/platform/graphics/harfbuzz/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.
  *     * Redistributions in binary form must reproduce the above
  * copyright notice, this list of conditions and the following disclaimer
  * in the documentation and/or other materials provided with the
@@ skipping 488 matching lines @@
 void HarfBuzzShaper::setFontFeatures()
 {
     const FontDescription& description = m_font->fontDescription();
     if (description.orientation() == Vertical) {
         static hb_feature_t vert = { HarfBuzzFace::vertTag, 1, 0, static_cast<unsigned>(-1) };
         static hb_feature_t vrt2 = { HarfBuzzFace::vrt2Tag, 1, 0, static_cast<unsigned>(-1) };
         m_features.append(vert);
         m_features.append(vrt2);
     }
 
+    static const hb_tag_t kernTag = HB_TAG('k', 'e', 'r', 'n');
+    static hb_feature_t kern = { kernTag, 1, 0, static_cast<unsigned>(-1) };
+    static hb_feature_t noKern = { kernTag, 0, 0, static_cast<unsigned>(-1) };
+    switch (description.kerning()) {
+    case FontDescription::NormalKerning:
+        m_features.append(kern);

[behdad_google, 2013/11/15 22:16:37]

No need to explicitly turn on.  Default is turned on.  Adding it pollutes /
disables hb's internal cache.

+        break;
+    case FontDescription::NoneKerning:
+        m_features.append(noKern);
+        break;
+    case FontDescription::AutoKerning:
+        break;
+    }
+
     FontFeatureSettings* settings = description.featureSettings();
     if (!settings)
         return;
 
     unsigned numFeatures = settings->size();
     for (unsigned i = 0; i < numFeatures; ++i) {
         hb_feature_t feature;
         String tag = settings->at(i).tag();
         feature.tag = HB_TAG(tag[0], tag[1], tag[2], tag[3]);
         feature.value = settings->at(i).value();
@@ skipping 353 matching lines @@
     if (!foundToX)
         toX = m_run.rtl() ? 0 : m_totalWidth;
 
     // Using floorf() and roundf() as the same as mac port.
     if (fromX < toX)
         return FloatRect(floorf(point.x() + fromX), point.y(), roundf(toX - fromX), height);
     return FloatRect(floorf(point.x() + toX), point.y(), roundf(fromX - toX), height);
 }
 
 } // namespace WebCore