Give structured information about imports and export in the service's library response.

runtime/observatory/tests/service/library_dependency_test.dart

+// Copyright (c) 2015, 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.
+// VMOptions=--compile-all --error_on_bad_type --error_on_bad_override
+
+import 'package:observatory/service_io.dart';
+import 'package:observatory/debugger.dart';
+import 'package:unittest/unittest.dart';
+import 'test_helper.dart';
+import 'dart:async';
+
+export 'dart:collection';
+import 'dart:mirrors' as mirrors;
+import 'dart:convert' deferred as convert;
+
+var tests = [
+
+(Isolate isolate) async {
+  var lib = await isolate.rootLibrary.load();
+
+  importOf(String uri) {
+    return lib.dependencies.singleWhere((dep) => dep.target.uri == uri);
+  }
+
+  expect(importOf("dart:collection").isImport, isFalse);
+  expect(importOf("dart:collection").isExport, isTrue);
+  expect(importOf("dart:collection").isDeferred, isFalse);
+  expect(importOf("dart:collection").prefix, equals(null));
+
+  expect(importOf("dart:mirrors").isImport, isTrue);
+  expect(importOf("dart:mirrors").isExport, isFalse);
+  expect(importOf("dart:mirrors").isDeferred, isFalse);
+  expect(importOf("dart:mirrors").prefix, equals("mirrors"));
+
+  expect(importOf("dart:convert").isImport, isTrue);
+  expect(importOf("dart:convert").isExport, isFalse);
+  expect(importOf("dart:convert").isDeferred, isTrue);
+  expect(importOf("dart:convert").prefix, equals("convert"));
+},
+];
+
+main(args) => runIsolateTests(args, tests);