Implement DeclarationMirror.location for all but ParameterMirrors.

tests/lib/mirrors/library_with_annotated_declaration.dart

Index: tests/lib/mirrors/library_with_annotated_declaration.dart
diff --git a/runtime/observatory/lib/cli.dart b/tests/lib/mirrors/library_with_annotated_declaration.dart
similarity index 62%
copy from runtime/observatory/lib/cli.dart
copy to tests/lib/mirrors/library_with_annotated_declaration.dart
index 607c58a919685c7fca635c1bf5acb02543720582..eeff40d1df7840971fc77fe189c52c493f0abfba 100644
--- a/runtime/observatory/lib/cli.dart
+++ b/tests/lib/mirrors/library_with_annotated_declaration.dart
@@ -2,8 +2,9 @@
 // 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 cli;
+@metadata
+library library_with_annotated_declaration;
 
-import 'dart:async';
+const metadata = 'metadata';
 
-part 'src/cli/command.dart';
+class ClassInLibraryWithAnnotatedDeclaration {}