Update V8 to r6101 as required by WebKit r74534

Change-Id: I7f84af8dd732f11898fd644b2c2b1538914cb78d
diff --git a/src/string-stream.h b/src/string-stream.h
index 323a6d6..b3f2e0d 100644
--- a/src/string-stream.h
+++ b/src/string-stream.h
@@ -138,10 +138,12 @@
            FmtElm arg3);
 
   // Getting the message out.
-  void OutputToStdOut();
+  void OutputToFile(FILE* out);
+  void OutputToStdOut() { OutputToFile(stdout); }
   void Log();
   Handle<String> ToString();
   SmartPointer<const char> ToCString() const;
+  int length() const { return length_; }
 
   // Object printing support.
   void PrintName(Object* o);