Fix analyzer warning.

pkg/analysis_server/lib/src/domain_context.dart

Index: pkg/analysis_server/lib/src/domain_context.dart
diff --git a/pkg/analysis_server/lib/src/domain_context.dart b/pkg/analysis_server/lib/src/domain_context.dart
index 07e356758d1782c321383ec79a8c76bca599436a..d7ff3ff83d60c933208b020aa3fbf39f9a70d7c8 100644
--- a/pkg/analysis_server/lib/src/domain_context.dart
+++ b/pkg/analysis_server/lib/src/domain_context.dart
@@ -265,11 +265,13 @@ class ContextDomainHandler implements RequestHandler {
    * the specified context does not exist.
    */
   AnalysisContext getAnalysisContext(Request request) {
-    String contextId = request.getRequiredParameter(CONTEXT_ID_PARAM).asString();
-    AnalysisContext context = server.contextMap[contextId];
-    if (context == null) {
-      throw new RequestFailure(new Response.contextDoesNotExist(request));
-    }
-    return context;
+    // TODO(scheglov) remove it after migrating to the new API
+    return null;
+//    String contextId = request.getRequiredParameter(CONTEXT_ID_PARAM).asString();
+//    AnalysisContext context = server.contextMap[contextId];
+//    if (context == null) {
+//      throw new RequestFailure(new Response.contextDoesNotExist(request));
+//    }
+//    return context;
   }
 }