Remove redundant context lookups from option-processing code.

pkg/analysis_server/test/context_manager_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 test.context.directory.manager;
 
 import 'dart:collection';
 
 import 'package:analysis_server/src/context_manager.dart';
 import 'package:analyzer/file_system/file_system.dart';
@@ skipping 125 matching lines @@
     manager.setRoots(<String>[projPath], <String>[], <String, String>{});
     expect(manager.isInAnalysisRoot('/test.dart'), isFalse);
   }
 
   test_path_filter() async {
     // Setup context.
     Folder root = resourceProvider.newFolder(projPath);
     manager.setRoots(<String>[projPath], <String>[], <String, String>{});
     expect(callbacks.currentContextFilePaths[projPath], isEmpty);
     // Set ignore patterns for context.
+    ContextInfo rootInfo = manager.getContextInfoFor(root);
     manager.setIgnorePatternsForContext(
-        root, ['sdk_ext/**', 'lib/ignoreme.dart']);
+        rootInfo, ['sdk_ext/**', 'lib/ignoreme.dart']);
     // Start creating files.
     newFile([projPath, ContextManagerImpl.PUBSPEC_NAME]);
     String libPath = newFolder([projPath, LIB_NAME]);
     newFile([libPath, 'main.dart']);
     newFile([libPath, 'ignoreme.dart']);
     String sdkExtPath = newFolder([projPath, 'sdk_ext']);
     newFile([sdkExtPath, 'entry.dart']);
     String sdkExtSrcPath = newFolder([projPath, 'sdk_ext', 'src']);
     newFile([sdkExtSrcPath, 'part.dart']);
     // Pump event loop so new files are discovered and added to context.
@@ skipping 1403 matching lines @@
 class TestUriResolver extends UriResolver {
   Map<Uri, Source> uriMap;
 
   TestUriResolver(this.uriMap);
 
   @override
   Source resolveAbsolute(Uri uri) {
     return uriMap[uri];
   }
 }