Convert analysis server over to use ContextBuilder

pkg/analyzer/lib/file_system/memory_file_system.dart

Index: pkg/analyzer/lib/file_system/memory_file_system.dart
diff --git a/pkg/analyzer/lib/file_system/memory_file_system.dart b/pkg/analyzer/lib/file_system/memory_file_system.dart
index d179d7f523184133448de9af85162d5f6a82ae20..0ba9b9409dee7331c708bbbb286c5d2b4ea19141 100644
--- a/pkg/analyzer/lib/file_system/memory_file_system.dart
+++ b/pkg/analyzer/lib/file_system/memory_file_system.dart
@@ -201,6 +201,15 @@ class MemoryResourceProvider implements ResourceProvider {
     return file;
   }
 
+  /**
+   * Write a representation of the file system on the given [sink].
+   */
+  void writeOn(StringSink sink) {
+    List<String> paths = _pathToResource.keys.toList();
+    paths.sort();
+    paths.forEach(sink.writeln);
+  }
+
   void _checkFileAtPath(String path) {
     _MemoryResource resource = _pathToResource[path];
     if (resource is! _MemoryFile) {
@@ -484,6 +493,9 @@ class _MemoryFolder extends _MemoryResource implements Folder {
   }
 
   @override
+  Folder resolveSymbolicLinksSync() => this;
+
+  @override
   Uri toUri() =>
       new Uri.directory(path, windows: _provider.pathContext == windows);
 }