Fix input and output to handle UTF16 surrogate pairs.

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
===================================================================
--- src/hydrogen-instructions.h	(revision 10944)
+++ src/hydrogen-instructions.h	(working copy)
@@ -4283,7 +4283,7 @@
   virtual bool DataEquals(HValue* other) { return true; }
 
   virtual Range* InferRange(Zone* zone) {
-    return new(zone) Range(0, String::kMaxUC16CharCode);
+    return new(zone) Range(0, String::kMaxUtf16CodeUnit);
   }
 };