Remove unneeded constructor for CompositionUnderline

Source/core/editing/CompositionUnderline.h

Index: Source/core/editing/CompositionUnderline.h
diff --git a/Source/core/editing/CompositionUnderline.h b/Source/core/editing/CompositionUnderline.h
index a4bee710213620fa5e3bd3235bb74c6becc858f9..106ac867bbc0f6e2dea5652ccadc9629cfe54923 100644
--- a/Source/core/editing/CompositionUnderline.h
+++ b/Source/core/editing/CompositionUnderline.h
@@ -38,14 +38,6 @@ struct CompositionUnderline {
         , thick(false)
         , backgroundColor(Color::transparent) { }
 
-    // FIXME(huangs): remove this constructor.
-    CompositionUnderline(unsigned s, unsigned e, const Color& c, bool t)
-        : startOffset(s)
-        , endOffset(e)
-        , color(c)
-        , thick(t)
-        , backgroundColor(Color::transparent) { }
-
     CompositionUnderline(unsigned s, unsigned e, const Color& c, bool t, const Color& bc)
         : startOffset(s)
         , endOffset(e)