- Add missing AddProperty function, which was lost during reformatting.

runtime/vm/json_stream.h

Index: runtime/vm/json_stream.h
===================================================================
--- runtime/vm/json_stream.h	(revision 27346)
+++ runtime/vm/json_stream.h	(working copy)
@@ -103,6 +103,9 @@
   void AddProperty(const char* name, double d) const {
     stream_->PrintProperty(name, d);
   }
+  void AddProperty(const char* name, const char* s) const {
+    stream_->PrintProperty(name, s);
+  }
   void AddProperty(const char* name, const Object& obj, bool ref = true) const {
     stream_->PrintProperty(name, obj, ref);
   }