Track the region where text is painted.

Source/core/platform/graphics/mac/FontComplexTextMac.cpp

Index: Source/core/platform/graphics/mac/FontComplexTextMac.cpp
diff --git a/Source/core/platform/graphics/mac/FontComplexTextMac.cpp b/Source/core/platform/graphics/mac/FontComplexTextMac.cpp
index 7595e6efce2e856b32a7e0c0568486b485528855..7f5339b0f2f1593f3480fd3792f2a5422ebbac69 100644
--- a/Source/core/platform/graphics/mac/FontComplexTextMac.cpp
+++ b/Source/core/platform/graphics/mac/FontComplexTextMac.cpp
@@ -92,14 +92,14 @@ float Font::getGlyphsAndAdvancesForComplexText(const TextRun& run, int from, int
     return initialAdvance;
 }
 
-void Font::drawComplexText(GraphicsContext* context, const TextRun& run, const FloatPoint& point, int from, int to) const
+void Font::drawComplexText(GraphicsContext* context, const TextRun& run, const FloatPoint& point, const FloatRect& textRect, int from, int to) const
 {
     if (preferHarfBuzz(this)) {
         GlyphBuffer glyphBuffer;
         HarfBuzzShaper shaper(this, run);
         shaper.setDrawRange(from, to);
         if (shaper.shape(&glyphBuffer)) {
-            drawGlyphBuffer(context, run, glyphBuffer, point);
+            drawGlyphBuffer(context, run, glyphBuffer, point, textRect);
             return;
         }
     }
@@ -114,10 +114,10 @@ void Font::drawComplexText(GraphicsContext* context, const TextRun& run, const F
 
     // Draw the glyph buffer now at the starting point returned in startX.
     FloatPoint startPoint(startX, point.y());
-    drawGlyphBuffer(context, run, glyphBuffer, startPoint);
+    drawGlyphBuffer(context, run, glyphBuffer, startPoint, textRect);
 }
 
-void Font::drawEmphasisMarksForComplexText(GraphicsContext* context, const TextRun& run, const AtomicString& mark, const FloatPoint& point, int from, int to) const
+void Font::drawEmphasisMarksForComplexText(GraphicsContext* context, const TextRun& run, const AtomicString& mark, const FloatPoint& point, const FloatRect& textRect, int from, int to) const
 {
     GlyphBuffer glyphBuffer;
     float initialAdvance = getGlyphsAndAdvancesForComplexText(run, from, to, glyphBuffer, ForTextEmphasis);
@@ -125,7 +125,7 @@ void Font::drawEmphasisMarksForComplexText(GraphicsContext* context, const TextR
     if (glyphBuffer.isEmpty())
         return;
 
-    drawEmphasisMarks(context, run, glyphBuffer, mark, FloatPoint(point.x() + initialAdvance, point.y()));
+    drawEmphasisMarks(context, run, glyphBuffer, mark, FloatPoint(point.x() + initialAdvance, point.y()), textRect);
 }
 
 float Font::floatWidthForComplexText(const TextRun& run, HashSet<const SimpleFontData*>* fallbackFonts, GlyphOverflow* glyphOverflow) const