restructure client api to use streams

pkg/analysis_server/lib/src/protocol.dart

Index: pkg/analysis_server/lib/src/protocol.dart
diff --git a/pkg/analysis_server/lib/src/protocol.dart b/pkg/analysis_server/lib/src/protocol.dart
index 0d39c312dbf0a6811b826d9d7ca1661bf18ae985..d2f926b8c3fdf6d1e1af1dbe2c2fbf882f025698 100644
--- a/pkg/analysis_server/lib/src/protocol.dart
+++ b/pkg/analysis_server/lib/src/protocol.dart
@@ -265,8 +265,10 @@ class Response {
    */
   factory Response.fromJson(Map<String, Object> json) {
     try {
-      // TODO process result
       String id = json[Response.ID];
+      if (id == null) {
+        return null;

[Brian Wilkerson, 2014/03/01 17:16:37]

Would it be better to throw an exception? (Not sure, just asking.)

[danrubel, 2014/03/03 16:52:20]

I'm not sure either. Not in this CL, but this is something we should revisit.

+      }
       var error = json[Response.ERROR];
       var result = json[Response.RESULT];
       Response response;