Get rid of redundant MockSdk.

pkg/analyzer/test/generated/all_the_rest_test.dart

 // Copyright (c) 2014, 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.test.generated.all_the_rest_test;
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/file_system/physical_file_system.dart';
@@ skipping 3933 matching lines @@
     Source source = resolver.resolveAbsolute(uri);
     expect(source, isNotNull);
     expect(resolver.restoreAbsolute(source), uri);
     expect(
         resolver.restoreAbsolute(
             new NonExistingSource(source.fullName, null, null)),
         uri);
   }
 }
 
-/**
- * Instances of the class `MockDartSdk` implement a [DartSdk].
- */
-class MockDartSdk implements DartSdk {
-  @override
-  AnalysisContext get context => null;
-
-  @override
-  List<SdkLibrary> get sdkLibraries => null;
-
-  @override
-  String get sdkVersion => null;
-
-  @override
-  List<String> get uris => null;
-
-  @override
-  Source fromFileUri(Uri uri) => null;
-
-  @override
-  SdkLibrary getSdkLibrary(String dartUri) => null;
-
-  @override
-  Source mapDartUri(String dartUri) => null;
-}
-
 @reflectiveTest
 class SDKLibrariesReaderTest extends EngineTestCase {
   void test_readFrom_dart2js() {
     LibraryMap libraryMap = new SdkLibrariesReader(true).readFromFile(
         FileUtilities2.createFile("/libs.dart"),
         r'''
 final Map<String, LibraryInfo> LIBRARIES = const <String, LibraryInfo> {
   'first' : const LibraryInfo(
     'first/first.dart',
     categories: 'Client',
@@ skipping 70 matching lines @@
     expect(UriKind.fromEncoding(0x70), same(UriKind.PACKAGE_URI));
     expect(UriKind.fromEncoding(0x58), same(null));
   }
 
   void test_getEncoding() {
     expect(UriKind.DART_URI.encoding, 0x64);
     expect(UriKind.FILE_URI.encoding, 0x66);
     expect(UriKind.PACKAGE_URI.encoding, 0x70);
   }
 }