Fix more strong mode errors in analyzer

pkg/analyzer/lib/src/task/yaml.dart

 // Copyright (c) 2016, 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 analyzer.src.task.yaml;
 
 import 'package:analyzer/src/context/cache.dart';
 import 'package:analyzer/src/dart/scanner/scanner.dart';
 import 'package:analyzer/src/generated/engine.dart' hide AnalysisTask;
 import 'package:analyzer/src/generated/error.dart';
@@ skipping 82 matching lines @@
       outputs[YAML_ERRORS] = errors;
       outputs[LINE_INFO] = new LineInfo.fromContent(content);
     }
   }
 
   /**
    * Return a map from the names of the inputs of this kind of task to the task
    * input descriptors describing those inputs for a task with the given
    * [source].
    */
-  static Map<String, TaskInput> buildInputs(Source source) {
+  static Map<String, TaskInput> buildInputs(AnalysisTarget source) {
     return <String, TaskInput>{CONTENT_INPUT_NAME: CONTENT.of(source)};
   }
 
   /**
    * Create a [ParseYamlTask] based on the given [target] in the given [context].
    */
   static ParseYamlTask createTask(
       AnalysisContext context, AnalysisTarget target) {
     return new ParseYamlTask(context, target);
   }
@@ skipping 32 matching lines @@
    */
   const YamlErrorCode(String name, String message, [String correction])
       : super(name, message, correction);
 
   @override
   ErrorSeverity get errorSeverity => ErrorSeverity.ERROR;
 
   @override
   ErrorType get type => ErrorType.COMPILE_TIME_ERROR;
 }