Track the region where text is painted.

Source/core/platform/graphics/Font.cpp

Index: Source/core/platform/graphics/Font.cpp
diff --git a/Source/core/platform/graphics/Font.cpp b/Source/core/platform/graphics/Font.cpp
index 235be5a0456f21e18e53894f7b81edfab73b9786..40607b94b7a978b4775325ac77c5495b08a4adeb 100644
--- a/Source/core/platform/graphics/Font.cpp
+++ b/Source/core/platform/graphics/Font.cpp
@@ -156,7 +156,7 @@ void Font::update(PassRefPtr<FontSelector> fontSelector) const
     m_typesettingFeatures = computeTypesettingFeatures();
 }
 
-void Font::drawText(GraphicsContext* context, const TextRun& run, const FloatPoint& point, int from, int to, CustomFontNotReadyAction customFontNotReadyAction) const
+void Font::drawText(GraphicsContext* context, const TextRun& run, const FloatPoint& point, const FloatRect& textRect, int from, int to, CustomFontNotReadyAction customFontNotReadyAction) const
 {
     // Don't draw anything while we are using custom fonts that are in the process of loading,
     // except if the 'force' argument is set to true (in which case it will use a fallback
@@ -172,12 +172,12 @@ void Font::drawText(GraphicsContext* context, const TextRun& run, const FloatPoi
         codePathToUse = Complex;
 
     if (codePathToUse != Complex)
-        return drawSimpleText(context, run, point, from, to);
+        return drawSimpleText(context, run, point, textRect, from, to);
 
-    return drawComplexText(context, run, point, from, to);
+    return drawComplexText(context, run, point, textRect, from, to);
 }
 
-void Font::drawEmphasisMarks(GraphicsContext* context, const TextRun& run, const AtomicString& mark, const FloatPoint& point, int from, int to) const
+void Font::drawEmphasisMarks(GraphicsContext* context, const TextRun& run, const AtomicString& mark, const FloatPoint& point, const FloatRect& textRect, int from, int to) const
 {
     if (loadingCustomFonts())
         return;
@@ -191,9 +191,9 @@ void Font::drawEmphasisMarks(GraphicsContext* context, const TextRun& run, const
         codePathToUse = Complex;
 
     if (codePathToUse != Complex)
-        drawEmphasisMarksForSimpleText(context, run, mark, point, from, to);
+        drawEmphasisMarksForSimpleText(context, run, mark, point, textRect, from, to);
     else
-        drawEmphasisMarksForComplexText(context, run, mark, point, from, to);
+        drawEmphasisMarksForComplexText(context, run, mark, point, textRect, from, to);
 }
 
 float Font::width(const TextRun& run, HashSet<const SimpleFontData*>* fallbackFonts, GlyphOverflow* glyphOverflow) const