Add some user-friendly utility functions to pkg/analyzer_experimental.

pkg/analyzer_experimental/lib/src/analyzer_impl.dart

 // Copyright (c) 2013, 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.
-part of analyzer;
+
+library analyzer_impl;
+
+import 'dart:async';
+import 'dart:io';
+
+import 'generated/java_io.dart';
+import 'generated/engine.dart';
+import 'generated/error.dart';
+import 'generated/source_io.dart';
+import 'generated/sdk.dart';
+import 'generated/sdk_io.dart';
+import 'generated/ast.dart';
+import 'generated/element.dart';
+import '../options.dart';
 
 /// Analyzes single library [File].
-class _AnalyzerImpl {
+class AnalyzerImpl {
   final CommandLineOptions options;
   DartSdk sdk;
 
   ContentCache contentCache = new ContentCache();
   SourceFactory sourceFactory;
   AnalysisContext context;
 
   /// All [Source]s references by the analyzed library.
   final Set<Source> sources = new Set<Source>();
 
   /// All [AnalysisErrorInfo]s in the analyzed library.
   final List<AnalysisErrorInfo> errorInfos = new List<AnalysisErrorInfo>();
 
-  _AnalyzerImpl(CommandLineOptions this.options) {
+  AnalyzerImpl(CommandLineOptions this.options) {
     sdk = new DirectoryBasedDartSdk(new JavaFile(options.dartSdkPath));
   }
 
   /**
    * Treats the [sourcePath] as the top level library and analyzes it.
    */
   void analyze(String sourcePath) {
     sources.clear();
     errorInfos.clear();
     if (sourcePath == null) {
@@ skipping 93 matching lines @@
 
   static JavaFile getPackageDirectoryFor(JavaFile sourceFile) {
     JavaFile sourceFolder = sourceFile.getParentFile();
     JavaFile packagesFolder = new JavaFile.relative(sourceFolder, "packages");
     if (packagesFolder.exists()) {
       return packagesFolder;
     }
     return null;
   }
 }