Revert of TextRun::length() should return an unsigned

Source/platform/fonts/Font.cpp

Index: Source/platform/fonts/Font.cpp
diff --git a/Source/platform/fonts/Font.cpp b/Source/platform/fonts/Font.cpp
index ce2503fec478398de6990aca9f6332df5ebdae8c..2aca587e3924ba04b548f1afc031d91c538b9dfa 100644
--- a/Source/platform/fonts/Font.cpp
+++ b/Source/platform/fonts/Font.cpp
@@ -178,7 +178,7 @@
     return result;
 }
 
-float Font::width(const TextRun& run, unsigned& charsConsumed, Glyph& glyphId) const
+float Font::width(const TextRun& run, int& charsConsumed, Glyph& glyphId) const
 {
 #if ENABLE(SVG_FONTS)
     if (TextRun::RenderingContext* renderingContext = run.renderingContext())
@@ -279,8 +279,6 @@
 FloatRect Font::selectionRectForText(const TextRun& run, const FloatPoint& point, int h, int from, int to, bool accountForGlyphBounds) const
 {
     to = (to == -1 ? run.length() : to);
-    ASSERT(from >= 0);
-    ASSERT(to >= 0);
 
     TextRunPaintInfo runInfo(run);
     runInfo.from = from;