Change SimpleShaper::advance to take unsigned

Source/platform/fonts/SimpleShaper.h

Index: Source/platform/fonts/SimpleShaper.h
diff --git a/Source/platform/fonts/SimpleShaper.h b/Source/platform/fonts/SimpleShaper.h
index 09d7dec437449532b1b3752095e6489de0847a02..d942d6ed279a8bd380916cf6a831cd90e59c79ec 100644
--- a/Source/platform/fonts/SimpleShaper.h
+++ b/Source/platform/fonts/SimpleShaper.h
@@ -43,7 +43,7 @@ struct PLATFORM_EXPORT SimpleShaper {
 public:
     SimpleShaper(const Font*, const TextRun&, HashSet<const SimpleFontData*>* fallbackFonts = 0, bool accountForGlyphBounds = false, bool forTextEmphasis = false);
 
-    unsigned advance(int to, GlyphBuffer* = 0);
+    unsigned advance(unsigned to, GlyphBuffer* = 0);
     bool advanceOneCharacter(float& width);
 
     float maxGlyphBoundingBoxY() const { ASSERT(m_accountForGlyphBounds); return m_maxGlyphBoundingBoxY; }