Allow Dart code to register service protocol handlers

runtime/vm/json_stream.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/assert.h"
 
 #include "vm/dart_entry.h"
 #include "vm/debugger.h"
 #include "vm/json_stream.h"
 #include "vm/message.h"
@@ skipping 85 matching lines @@
       return "Invalid params";
     case kInternalError:
       return "Internal error";
     case kFeatureDisabled:
       return "Feature is disabled";
     case kVMMustBePaused:
       return "VM must be paused";
     case kCannotAddBreakpoint:
       return "Cannot add breakpoint";
     default:
-      UNIMPLEMENTED();
-      return "Unexpected rpc error code";
+      return "Extension error";
   }
 }
 
 
 static void PrintRequest(JSONObject* obj, JSONStream* js) {
   JSONObject jsobj(obj, "request");
   jsobj.AddProperty("method", js->method());
   {
     JSONObject params(&jsobj, "params");
     for (intptr_t i = 0; i < js->num_params(); i++) {
@@ skipping 583 matching lines @@
   intptr_t len2 = OS::VSNPrint(p, len+1, format, args);
   va_end(args);
   ASSERT(len == len2);
   stream_->buffer_.AddChar('"');
   stream_->AddEscapedUTF8String(p);
   stream_->buffer_.AddChar('"');
   free(p);
 }
 
 }  // namespace dart