Add string encoding to wire protocol

tools/ddbg.dart

Index: tools/ddbg.dart
===================================================================
--- tools/ddbg.dart	(revision 8218)
+++ tools/ddbg.dart	(working copy)
@@ -39,6 +39,7 @@
   ll  List loaded libraries
   pl <id> Print dlibrary info for given id
   ls <libname> List loaded scripts in library
+  gs <lib_id> <script_url> Get source text of script in library
   h   Print help
 """);
 }
@@ -117,6 +118,11 @@
     var cmd = { "id": seqNum, "command": "getLibraryProperties",
                 "params": {"libraryId": Math.parseInt(args[1]) }};
     sendCmd(cmd).then((result) => handleGetLibraryPropsResponse(result));
+  } else if (command == "gs" && args.length == 3) {
+    var cmd = { "id": seqNum, "command":  "getScriptSource",
+                "params": { "libraryId": Math.parseInt(args[1]),
+                            "url": args[2] }};
+    sendCmd(cmd).then((result) => handleGetSourceResponse(result));
   } else if (command == "q") {
     quitShell();
   } else if (command == "h") {
@@ -197,6 +203,13 @@
 }
 
 
+handleGetSourceResponse(response) {
+  Map result = response["result"];
+  String source = result["text"];
+  print("Source text:\n$source\n--------");
+}
+
+
 void handleGetLibraryResponse(response) {
   Map result = response["result"];
   List libs = result["libraries"];