Add package root setting to analysis server API.

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 d3af4738fd6f5a6c4fa49cdc153641fd42dd3a5f..adeb2af46f6e8c8b3995e88e299a6172f2e341f8 100644
--- a/pkg/analysis_server/test/integration/protocol_matchers.dart
+++ b/pkg/analysis_server/test/integration/protocol_matchers.dart
@@ -159,12 +159,15 @@ final Matcher isAnalysisReanalyzeResult = isNull;
  * {
  *   "included": List<FilePath>
  *   "excluded": List<FilePath>
+ *   "packageRoots": optional Map<FilePath, FilePath>
  * }
  */
 final Matcher isAnalysisSetAnalysisRootsParams = new LazyMatcher(() => new MatchesJsonObject(
   "analysis.setAnalysisRoots params", {
     "included": isListOf(isFilePath),
     "excluded": isListOf(isFilePath)
+  }, optionalFields: {
+    "packageRoots": isMapOf(isFilePath, isFilePath)
   }));
 
 /**