Add package root setting to analysis server API.

pkg/analysis_server/lib/src/protocol.dart

 // Copyright (c) 2014, 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.
 
 library protocol;
 
 import 'dart:collection';
 import 'dart:convert';
 
 part 'generated_protocol.dart';
@@ skipping 111 matching lines @@
     }
   }
   return true;
 }
 
 /**
  * Compare the maps [mapA] and [mapB], using [valueEqual] to compare map
  * values.
  */
 bool _mapEqual(Map mapA, Map mapB, bool valueEqual(a, b)) {
+  if (mapA == null) {
+    return mapB == null;
+  }
+  if (mapB == null) {
+    return false;
+  }
   if (mapA.length != mapB.length) {
     return false;
   }
   for (var key in mapA.keys) {
     if (!mapB.containsKey(key)) {
       return false;
     }
     if (!valueEqual(mapA[key], mapB[key])) {
       return false;
     }
@@ skipping 704 matching lines @@
     hash = 0x1fffffff & (hash + ((0x03ffffff & hash) << 3));
     hash = hash ^ (hash >> 11);
     return 0x1fffffff & (hash + ((0x00003fff & hash) << 15));
   }
 
   static int hash2(a, b) => finish(combine(combine(0, a), b));
 
   static int hash4(a, b, c, d) =>
       finish(combine(combine(combine(combine(0, a), b), c), d));
 }