Support more debugger commands in the wire protocol

runtime/platform/json.h

Index: runtime/platform/json.h
===================================================================
--- runtime/platform/json.h	(revision 7517)
+++ runtime/platform/json.h	(working copy)
@@ -88,6 +88,7 @@
   int ValueLen() const {
     return (Type() != kNone) ? scanner_.TokenLen() : 0;
   }
+  void GetValueChars(char* buf, intptr_t buflen) const;
   bool IsStringLiteral(const char* literal) const {
     return scanner_.IsStringLiteral(literal);
   }
@@ -116,6 +117,8 @@
   ~TextBuffer();
 
   intptr_t Printf(const char* format, ...);
+  intptr_t Printf(const char* format, va_list args);
+
   void Clear();
 
   char* buf() { return buf_; }