Add Unicode Variation Selector support to harfBuzzGetGlyph

Source/platform/fonts/shaping/HarfBuzzShaperTest.cpp

 // Copyright (c) 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 "config.h"
 #include "platform/fonts/shaping/HarfBuzzShaper.h"
 
 #include "platform/fonts/Font.h"
 #include "platform/fonts/FontCache.h"
 #include "platform/fonts/GlyphPage.h"
@@ skipping 67 matching lines @@
         { "Not-defined Variants", { 0x41, 0xDB40, 0xDDEF }, HB_SCRIPT_LATIN },
     };
     for (auto& test : testlist) {
         String str(test.string);
         TextRun run(str);
         HarfBuzzShaper shaper(font, run);
         shaper.shape();
         EXPECT_EQ(1u, shaper.numberOfRunsForTesting()) << test.name;
         ASSERT_TRUE(shaper.runInfoForTesting(0, startIndex, numGlyphs, script)) << test.name;
         EXPECT_EQ(0u, startIndex) << test.name;
-        // TODO(kojii): HarfBuzzFace does not support UVS yet and numGlyphs becomes 2
-        // EXPECT_EQ(1u, numGlyphs) << test.name;
+        if (numGlyphs == 2) {
+            // If the specified VS is not in the font, it's mapped to .notdef.
+            // then hb_ot_hide_default_ignorables() swaps it to a space with zero-advance.
+            // http://lists.freedesktop.org/archives/harfbuzz/2015-May/004888.html
+            // OpenType recommends Glyph ID 3 for a space; not a hard requirement though.
+            // https://www.microsoft.com/typography/otspec/recom.htm
+#if !OS(MACOSX)
+            EXPECT_EQ(3u, shaper.glyphForTesting(0, 1)) << test.name;
+#endif
+            EXPECT_EQ(0.f, shaper.advanceForTesting(0, 1)) << test.name;
+        } else {
+            EXPECT_EQ(1u, numGlyphs) << test.name;
+        }
         EXPECT_EQ(test.script, script) << test.name;
     }
 }
 
 TEST_F(HarfBuzzShaperTest, ResolveCandidateRunsDevanagariCommon)
 {
     UChar devanagariCommonString[] = { 0x915, 0x94d, 0x930, 0x28, 0x20, 0x29 };
     TextRun devanagariCommonLatin(devanagariCommonString, 6);
     HarfBuzzShaper shaper(font, devanagariCommonLatin);
     shaper.shape();
@@ skipping 71 matching lines @@
     shaper.shape();
 
     EXPECT_EQ(1u, shaper.numberOfRunsForTesting());
     ASSERT_TRUE(shaper.runInfoForTesting(0, startIndex, numGlyphs, script));
     EXPECT_EQ(0u, startIndex);
     EXPECT_EQ(3u, numGlyphs);
     EXPECT_EQ(HB_SCRIPT_ARABIC, script);
 }
 
 } // namespace blink