Add Unicode Variation Selector support to harfBuzzGetGlyph

LayoutTests/fast/text/unicode-variation-selector-expected.html

Index: LayoutTests/fast/text/unicode-variation-selector-expected.html
diff --git a/LayoutTests/fast/text/unicode-variation-selector.html b/LayoutTests/fast/text/unicode-variation-selector-expected.html
similarity index 55%
copy from LayoutTests/fast/text/unicode-variation-selector.html
copy to LayoutTests/fast/text/unicode-variation-selector-expected.html
index 1d9e563d407a2989304a8fcfb9482fc413ec46ee..1495dbcc2e9b3d7932bf2294d3d17ea8e064b5d4 100644
--- a/LayoutTests/fast/text/unicode-variation-selector.html
+++ b/LayoutTests/fast/text/unicode-variation-selector-expected.html
@@ -1,20 +1,23 @@
 <style>
-@font-face {
-    font-family: ivsfont;
-    src: url(resources/AhemIVS.ttf);
-}
-.ivs {
-    font-family: ivsfont;
+.ahem {
+    font:20px/1 Ahem;
 }
 </style>
 <p>
 This page ensures that WebKit can render unicode variation selector correctly.  On platforms which support UVSes, the glyph of U+0061 should be a 0.2em high, 1em wide rectangle. On platforms which don't support UVSes, it should be a square.  In addition, any glyphs (including the last resort glyph) should not appear after the glyph on all platforms.
 </p>
 <div>
-Glyph for code point U+0061 without UVS:
-<span style="font-family: ivsfont;">&#x0061;</span>
+Without UVS:
+<span class="ahem">X</span>
+should look like <span class="ahem">X</span>
+</div>
+<div>
+With UVS:
+<span class="ahem">p</span>
+should look like <span class="ahem">p</span>
 </div>
 <div>
-Glyph for code point U+0061 with UVS:
-<span style="font-family: ivsfont;" id='ivs-holder'>&#x0061;&#xE0100;</span>
+UVS not in the font should fallback to base:
+<span class="ahem">X</span>
+should look like <span class="ahem">X</span>
 </div>