pkg/docgen: moved model classes into minilibs

pkg/docgen/lib/src/models/annotation.dart

+library docgen.models.annotation;
+
+import '../exports/mirrors_util.dart' as dart2js_util;
+import '../exports/source_mirrors.dart';
+
+import '../library_helpers.dart';
+
+import 'library.dart';
+import 'mirror_based.dart';
+
+/// Holds the name of the annotation, and its parameters.
+class Annotation extends MirrorBased {
+  /// The class of this annotation.
+  final ClassMirror mirror;
+  final Library owningLibrary;
+  List<String> parameters;
+
+  Annotation(InstanceMirror originalMirror, this.owningLibrary)
+      : mirror = originalMirror.type {
+    parameters = dart2js_util.variablesOf(originalMirror.type.declarations)
+        .where((e) => e.isFinal)
+        .map((e) => originalMirror.getField(e.simpleName).reflectee)
+        .where((e) => e != null)
+        .toList();
+  }
+
+  Map toMap() => {
+    'name': getDocgenObject(mirror, owningLibrary).docName,
+    'parameters': parameters
+  };
+}