Implement CSS Emphasis Marks for complex text

Source/platform/fonts/harfbuzz/FontHarfBuzz.cpp

Index: Source/platform/fonts/harfbuzz/FontHarfBuzz.cpp
diff --git a/Source/platform/fonts/harfbuzz/FontHarfBuzz.cpp b/Source/platform/fonts/harfbuzz/FontHarfBuzz.cpp
index f4ffeb69c837e033630dc02acf4eb50d54b1cb16..a9eca7e6a046ab5cf1a0d1731e9d4d3cb33eabb0 100644
--- a/Source/platform/fonts/harfbuzz/FontHarfBuzz.cpp
+++ b/Source/platform/fonts/harfbuzz/FontHarfBuzz.cpp
@@ -185,9 +185,27 @@ void Font::drawComplexText(GraphicsContext* gc, const TextRunPaintInfo& runInfo,
     drawGlyphBuffer(gc, runInfo, glyphBuffer, adjustedPoint);
 }
 
-void Font::drawEmphasisMarksForComplexText(GraphicsContext* /* context */, const TextRunPaintInfo& /* runInfo */, const AtomicString& /* mark */, const FloatPoint& /* point */) const
+void Font::drawEmphasisMarksForComplexText(GraphicsContext* context, const TextRunPaintInfo& runInfo, const AtomicString& mark, const FloatPoint& point) const
 {
-    notImplemented();
+    GlyphBuffer glyphBuffer;
+
+    float initialAdvance = getGlyphsAndAdvancesForComplexText(runInfo.run, runInfo.from, runInfo.to, glyphBuffer, ForTextEmphasis);
+
+    if (glyphBuffer.isEmpty())
+        return;
+
+    drawEmphasisMarks(context, runInfo, glyphBuffer, mark, FloatPoint(point.x() + initialAdvance, point.y()));
+}
+
+float Font::getGlyphsAndAdvancesForComplexText(const TextRun& run, int from, int to, GlyphBuffer& glyphBuffer, ForTextEmphasisOrNot forTextEmphasis) const
+{
+    HarfBuzzShaper shaper(this, run, ForTextEmphasis); // TODO: forTextEmphasis argument? Nullify space & separator glyphs
+    shaper.setDrawRange(from, to);
+    if (!shaper.shape(&glyphBuffer))
+        return 0;
+
+    // TODO: rtl()? Get this initial value?
+    return 0;
 }
 
 float Font::floatWidthForComplexText(const TextRun& run, HashSet<const SimpleFontData*>* /* fallbackFonts */, GlyphOverflow* /* glyphOverflow */) const