More strong mode changes to analysis_server

pkg/analysis_server/benchmark/integration/log_file_input_converter.dart

Index: pkg/analysis_server/benchmark/integration/log_file_input_converter.dart
diff --git a/pkg/analysis_server/benchmark/integration/log_file_input_converter.dart b/pkg/analysis_server/benchmark/integration/log_file_input_converter.dart
index ba98b3b11714c4029c212c726113065ac77748c9..3490860dee19f3abeba8f08f7945d9316b522965 100644
--- a/pkg/analysis_server/benchmark/integration/log_file_input_converter.dart
+++ b/pkg/analysis_server/benchmark/integration/log_file_input_converter.dart
@@ -32,14 +32,14 @@ class LogFileInputConverter extends CommonInputConverter {
       String timeStampString = _parseTimeStamp(line);
       String data = line.substring(timeStampString.length);
       if (data.startsWith(RECEIVED_FRAGMENT)) {
-        Map<String, dynamic> json = JSON.decode(data.substring(4));
+        Map<String, dynamic> json = asMap(JSON.decode(data.substring(4)));
         if (json.containsKey('event')) {
           return convertNotification(json);
         } else {
           return convertResponse(json);
         }
       } else if (data.startsWith(SENT_FRAGMENT)) {
-        Map<String, dynamic> json = JSON.decode(data.substring(4));
+        Map<String, dynamic> json = asMap(JSON.decode(data.substring(4)));
         if (json.containsKey('method')) {
           return convertRequest(json);
         }