Add Unicode Variation Selector support to harfBuzzGetGlyph on Linux

Source/platform/fonts/shaping/HarfBuzzFace.cpp

 /*
  * Copyright (c) 2012 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:
  *
  *     * 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
@@ skipping 175 matching lines @@
         extents->width = SkiaScalarToHarfBuzzPosition(skBounds.width());
         extents->height = SkiaScalarToHarfBuzzPosition(-skBounds.height());
     }
 }
 
 static hb_bool_t harfBuzzGetGlyph(hb_font_t* hbFont, void* fontData, hb_codepoint_t unicode, hb_codepoint_t variationSelector, hb_codepoint_t* glyph, void* userData)
 {
     HarfBuzzFontData* hbFontData = reinterpret_cast<HarfBuzzFontData*>(fontData);
 
     if (variationSelector) {
-#if OS(LINUX)
-        // TODO(kojii): Linux non-official builds cannot use new HB APIs
-        // until crbug.com/462689 resolved or pangoft2 updates its HB.
-        return false;
-#else
         // Skia does not support variation selectors, but hb does.
         // We're not fully ready to switch to hb-ot-font yet,
         // but are good enough to get glyph IDs for OpenType fonts.
         if (!hbFontData->m_hbOpenTypeFont) {
             hbFontData->m_hbOpenTypeFont = hb_font_create(hbFontData->m_face);
             hb_ot_font_set_funcs(hbFontData->m_hbOpenTypeFont);
         }
         return hb_font_get_glyph(hbFontData->m_hbOpenTypeFont, unicode, variationSelector, glyph);
         // When not found, glyph_func should return false rather than fallback to the base.
         // http://lists.freedesktop.org/archives/harfbuzz/2015-May/004888.html
-#endif
     }
 
     WTF::HashMap<uint32_t, uint16_t>::AddResult result = hbFontData->m_glyphCacheForFaceCacheEntry->add(unicode, 0);
     if (result.isNewEntry) {
         SkPaint* paint = &hbFontData->m_paint;
         paint->setTextEncoding(SkPaint::kUTF32_TextEncoding);
         uint16_t glyph16;
         paint->textToGlyphs(&unicode, sizeof(hb_codepoint_t), &glyph16);
         result.storedValue->value = glyph16;
         *glyph = glyph16;
@@ skipping 144 matching lines @@
     hb_font_t* font = hb_font_create(m_face);
     hb_font_set_funcs(font, harfBuzzSkiaGetFontFuncs(), hbFontData, destroyHarfBuzzFontData);
     float size = m_platformData->size();
     int scale = SkiaScalarToHarfBuzzPosition(size);
     hb_font_set_scale(font, scale, scale);
     hb_font_make_immutable(font);
     return font;
 }
 
 } // namespace blink