Add support for getting the sessionId from instrumentation and sending it to the client

pkg/analysis_server/test/integration/protocol_matchers.dart

Index: pkg/analysis_server/test/integration/protocol_matchers.dart
diff --git a/pkg/analysis_server/test/integration/protocol_matchers.dart b/pkg/analysis_server/test/integration/protocol_matchers.dart
index 5c8e84a6ac3bf38b5eb16d996d2f96116f4576a7..fef9ef3fab5523bd512581bab88f76fffa78faca 100644
--- a/pkg/analysis_server/test/integration/protocol_matchers.dart
+++ b/pkg/analysis_server/test/integration/protocol_matchers.dart
@@ -66,12 +66,15 @@ final Matcher isServerSetSubscriptionsResult = isNull;
  * {
  *   "version": String
  *   "pid": int
+ *   "sessionId": optional String
  * }
  */
 final Matcher isServerConnectedParams = new LazyMatcher(() => new MatchesJsonObject(
   "server.connected params", {
     "version": isString,
     "pid": isInt
+  }, optionalFields: {
+    "sessionId": isString
   }));
 
 /**