Use package names as import prefixes when generating code

lib/enum_generator.dart

 // Copyright (c) 2013, 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.
 
 part of protoc;
 
 class EnumAlias {
   final EnumValueDescriptorProto value;
   final EnumValueDescriptorProto canonicalValue;
   EnumAlias(this.value, this.canonicalValue);
 }
 
 class EnumGenerator implements ProtobufContainer {
+  final ProtobufContainer _parent;
   final String classname;
   final String fqname;
   final List<EnumValueDescriptorProto> _canonicalValues =
       <EnumValueDescriptorProto>[];
   final List<EnumAlias> _aliases = <EnumAlias>[];
 
   EnumGenerator(
       EnumDescriptorProto descriptor,
       ProtobufContainer parent,
       GenerationContext context)
-    : classname = (parent == null || parent is FileGenerator) ?
+    : _parent = parent,
+      classname = (parent == null || parent is FileGenerator) ?
           descriptor.name : '${parent.classname}_${descriptor.name}',
       fqname = (parent == null || parent.fqname == null) ? descriptor.name :
           (parent.fqname == '.' ?
               '.${descriptor.name}' : '${parent.fqname}.${descriptor.name}') {
     for (EnumValueDescriptorProto value in descriptor.value) {
       EnumValueDescriptorProto canonicalValue =
           descriptor.value.firstWhere((v) => v.number == value.number);
       if (value == canonicalValue) {
         _canonicalValues.add(value);
       } else {
         _aliases.add(new EnumAlias(value, canonicalValue));
       }
     }
     context.register(this);
   }
 
+  String get package => _parent.package;
+
   void generate(IndentingWriter out) {
     out.addBlock('class ${classname} extends ProtobufEnum {', '}\n', () {
       // -----------------------------------------------------------------
       // Define enum types.
       for (EnumValueDescriptorProto val in _canonicalValues) {
         out.println(
             'static const ${classname} ${val.name}${SP}=${SP}'
                 "const ${classname}._(${val.number},${SP}'${val.name}');");
       }
       if (!_aliases.isEmpty) {
@@ skipping 18 matching lines @@
           '${SP}ProtobufEnum.initByValue(values);');
       out.println('static ${classname} valueOf(int value)${SP}=>'
           '${SP}_byValue[value];');
       out.println();
 
       out.println('const ${classname}._(int v,${SP}String n)${SP}'
           ':${SP}super(v,${SP}n);');
     });
   }
 }