Use real "package:" imports in pub's plugin-loading code.

sdk/lib/_internal/pub/asset/dart/transformer_isolate.dart

 // Copyright (c) 2014, 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.
 
-// Note: this explicitly avoids using a library tag because pub will add
-// additional imports at the top of the file.
+library pub.transformer_isolate;
 
 import 'dart:async';
 import 'dart:isolate';
 import 'dart:convert';
 import 'dart:mirrors';
 
-import '<<URL_BASE>>/packages/source_maps/span.dart';
-import '<<URL_BASE>>/packages/stack_trace/stack_trace.dart';
-import '<<URL_BASE>>/packages/barback/barback.dart';
+import 'package:source_maps/span.dart';
+import 'package:stack_trace/stack_trace.dart';
+import 'package:barback/barback.dart';
 // TODO(nweiz): don't import from "src" once issue 14966 is fixed.
-import '<<URL_BASE>>/packages/barback/src/internal_asset.dart';
+import 'package:barback/src/internal_asset.dart';
 
 /// Sets up the initial communication with the host isolate.
-void main(_, SendPort replyTo) {
+void loadTransformers(SendPort replyTo) {
   var port = new ReceivePort();
   replyTo.send(port.sendPort);
   port.first.then((wrappedMessage) {
     _respond(wrappedMessage, (message) {
       var library = Uri.parse(message['library']);
       var configuration = JSON.decode(message['configuration']);
       var mode = new BarbackMode(message['mode']);
-      return initialize(library, configuration, mode).
+      return _initialize(library, configuration, mode).
           map(_serializeTransformerOrGroup).toList();
     });
   });
 }
 
 /// Loads all the transformers and groups defined in [uri].
 ///
 /// Loads the library, finds any Transformer or TransformerGroup subclasses in
 /// it, instantiates them with [configuration] and [mode], and returns them.
-Iterable initialize(Uri uri, Map configuration, BarbackMode mode) {
+Iterable _initialize(Uri uri, Map configuration, BarbackMode mode) {
   var mirrors = currentMirrorSystem();
   var transformerClass = reflectClass(Transformer);
   var groupClass = reflectClass(TransformerGroup);
 
   // TODO(nweiz): if no valid transformers are found, throw an error message
   // describing candidates and why they were rejected.
   return mirrors.libraries[uri].declarations.values.map((declaration) {
     if (declaration is! ClassMirror) return null;
     var classMirror = declaration;
     if (classMirror.isPrivate) return null;
@@ skipping 53 matching lines @@
   }
 
   Future<String> readInputAsString(AssetId id, {Encoding encoding}) {
     if (encoding == null) encoding = UTF8;
     return getInput(id).then((input) => input.readAsString(encoding: encoding));
   }
 
   Stream<List<int>> readInput(AssetId id) =>
       _futureStream(getInput(id).then((input) => input.read()));
 
+  Future<bool> hasInput(AssetId id) {
+    return getInput(id).then((_) => true).catchError((error) {
+      if (error is AssetNotFoundException && error.id == id) return false;
+      throw error;
+    });
+  }
+
   void addOutput(Asset output) {
     _call(_port, {
       'type': 'addOutput',
       'output': serializeAsset(output)
     });
   }
+
+  void consumePrimary() {
+    _call(_port, {'type': 'consumePrimary'});
+  }
 }
 
 /// Returns the mirror for the root Object type.
 ClassMirror get objectMirror => reflectClass(Object);
 
 // TODO(nweiz): clean this up when issue 13248 is fixed.
 MethodMirror getConstructor(ClassMirror classMirror, String constructor) {
   var name = new Symbol("${MirrorSystem.getName(classMirror.simpleName)}"
       ".$constructor");
   var candidate = classMirror.declarations[name];
@@ skipping 253 matching lines @@
     subscription = callback().listen(controller.add,
         onError: controller.addError,
         onDone: controller.close);
   },
       onCancel: () => subscription.cancel(),
       onPause: () => subscription.pause(),
       onResume: () => subscription.resume(),
       sync: true);
   return controller.stream;
 }