Update UnitElementResult signature.

pkg/analyzer/lib/src/dart/analysis/driver.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.
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:typed_data';
 
 import 'package:analyzer/context/declared_variables.dart';
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 613 matching lines @@
         .add(completer);
     _scheduler.notify(this);
     return completer.future;
   }
 
   /**
    * Return a [Future] that completes with the signature for the
    * [UnitElementResult] for the file with the given [path], or with `null` if
    * the file cannot be analyzed.
    *
-   * The signature is based on the content of the file, and the transitive
-   * closure of files imported and exported by the the library of the requested
-   * file.
+   * The signature is based the APIs of the files of the library (including
+   * the file itself) of the requested file and the transitive closure of files
+   * imported and exported by the the library.
    */
   Future<String> getUnitElementSignature(String path) {
     if (!_fileTracker.fsState.hasUri(path)) {
       return new Future.value();
     }
     var completer = new Completer<String>();
     _unitElementSignatureRequests
         .putIfAbsent(path, () => <Completer<String>>[])
         .add(completer);
     _scheduler.notify(this);
@@ skipping 166 matching lines @@
     FileState file = _fileTracker.fsState.getFileForPath(path);
     FileState library = file.library ?? file;
 
     // Create the AnalysisContext to resynthesize elements in.
     LibraryContext libraryContext = _createLibraryContext(library);
 
     // Resynthesize the CompilationUnitElement in the context.
     try {
       CompilationUnitElement element =
           libraryContext.computeUnitElement(library.source, file.source);
-      String signature = _getResolvedUnitSignature(library, file);
+      String signature = library.transitiveSignature;
       return new UnitElementResult(path, file.contentHash, signature, element);
     } finally {
       libraryContext.dispose();
     }
   }
 
   String _computeUnitElementSignature(String path) {
     FileState file = _fileTracker.fsState.getFileForPath(path);
     FileState library = file.library ?? file;
-    return _getResolvedUnitSignature(library, file);
+    return library.transitiveSignature;
   }
 
   /**
    * Creates a new [FileTracker] object and stores it in [_fileTracker].
    *
    * This is used both on initial construction and whenever the configuration
    * changes.
    */
   void _createFileTracker(PerformanceLog logger) {
     _fillSalt();
@@ skipping 854 matching lines @@
    * The path of the file, absolute and normalized.
    */
   final String path;
 
   /**
    * The MD5 hash of the file content.
    */
   final String contentHash;
 
   /**
-   * The signature of the [element] based on the content of the file, and the
-   * transitive closure of files imported and exported by the the library of
-   * the requested file.
+   * The signature of the [element] is based the APIs of the files of the
+   * library (including the file itself) of the requested file and the
+   * transitive closure of files imported and exported by the the library.
    */
   final String signature;
 
   /**
    * The element of the file.
    */
   final CompilationUnitElement element;
 
   UnitElementResult(this.path, this.contentHash, this.signature, this.element);
 }
@@ skipping 183 matching lines @@
           libraryDeclarations.add(new TopLevelDeclarationInSource(
               file.source, declaration, isExported));
         }
       }
     }
 
     // We're not done yet.
     return false;
   }
 }