Don't re-read files when compute their analysis results.

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 524 matching lines @@
    * file with the given [path]. If the file is not a Dart file or cannot
    * be analyzed, the [Future] completes with `null`.
    *
    * The [path] must be absolute and normalized.
    *
    * The [path] can be any file - explicitly or implicitly analyzed, or neither.
    *
    * If the driver has the cached analysis result for the file, it is returned.
    *
    * Otherwise causes the analysis state to transition to "analyzing" (if it is
-   * not in that state already), the driver will read the file and produce the
-   * analysis result for it, which is consistent with the current file state
-   * (including the new state of the file), prior to the next time the analysis
-   * state transitions to "idle".
+   * not in that state already), the driver will produce the analysis result for
+   * it, which is consistent with the current file state (including new states
+   * of the files previously reported using [changeFile]), prior to the next
+   * time the analysis state transitions to "idle".
    */
   Future<AnalysisResult> getResult(String path) {
     if (!_fileTracker.fsState.hasUri(path)) {
       return new Future.value();
     }
 
     // Return the cached result.
     {
       AnalysisResult result = _priorityResults[path];
       if (result != null) {
@@ skipping 135 matching lines @@
       // Check for the cached result.
       String key = _getResolvedUnitKey(libraryFile, file);
       List<int> bytes = _byteStore.get(key);
       if (bytes != null) {
         return _getAnalysisResultFromBytes(file, bytes);
       }
     }
 
     // We need the fully resolved unit, or the result is not cached.
     return _logger.run('Compute analysis result for $path', () {
-      FileState file = _fileTracker.verifyApiSignature(path);
+      FileState file = fsState.getFileForPath(path);
 
       // Prepare the library file - the file itself, or the known library.
       FileState library = getLibraryFile(file);
       if (library == null) {
         return null;
       }
 
       try {
         LibraryContext libraryContext = _createLibraryContext(library);
         try {
@@ skipping 1071 matching lines @@
           libraryDeclarations.add(new TopLevelDeclarationInSource(
               file.source, declaration, isExported));
         }
       }
     }
 
     // We're not done yet.
     return false;
   }
 }