fix(dart/transform): Write correct ng_deps without deferred imports

Previously, the presence of a `deferred` import would cause us to output
incomplete `.ng_deps.dart` code.

Closes #4587

modules_dart/transform/test/transform/common/code/ng_deps_code_tests.dart

@@ -0,0 +1,51 @@
+library angular2.test.transform.common.code.ng_deps_code_tests;
+
+import 'package:analyzer/analyzer.dart';
+import 'package:angular2/src/transform/common/code/ng_deps_code.dart';
+import 'package:angular2/src/transform/common/model/import_export_model.pb.dart';
+import 'package:angular2/src/transform/common/model/ng_deps_model.pb.dart';
+import 'package:guinness/guinness.dart';
+
+main() => allTests();
+
+void allTests() {
+  describe('writeNgDepsModel', () {
+    it('should output parsable code', () async {
+      final ngDeps = new NgDepsModel()
+        ..libraryUri = 'test.foo'
+        ..imports.add(new ImportModel()
+          ..uri = 'bar.dart'
+          ..prefix = 'dep');
+
+      final buf = new StringBuffer();
+      final writer = new NgDepsWriter(buf);
+      writer.writeNgDepsModel(ngDeps);
+
+      var compilationUnit = parseCompilationUnit(buf.toString());
+
+      expect(compilationUnit).toBeNotNull();
+      expect(compilationUnit.declarations).toBeNotNull();
+      expect(compilationUnit.declarations.length > 0).toBeTrue();
+    });
+
+    it('should output parsable code with deferred imports', () async {
+      // Regression test for i/4587.
+      final ngDeps = new NgDepsModel()
+        ..libraryUri = 'test.foo'
+        ..imports.add(new ImportModel()
+          ..uri = 'bar.dart'
+          ..isDeferred = true
+          ..prefix = 'dep');
+
+      final buf = new StringBuffer();
+      final writer = new NgDepsWriter(buf);
+      writer.writeNgDepsModel(ngDeps);
+
+      var compilationUnit = parseCompilationUnit(buf.toString());
+
+      expect(compilationUnit).toBeNotNull();
+      expect(compilationUnit.declarations).toBeNotNull();
+      expect(compilationUnit.declarations.length > 0).toBeTrue();
+    });
+  });
+}