add from option to run

lib/src/mirror_loader.dart

Index: lib/src/mirror_loader.dart
diff --git a/lib/src/mirror_loader.dart b/lib/src/mirror_loader.dart
index c84721590658482a834bb58caa185ffef41122f6..c58f187c40527d0c768778605ef1b8354f5cc3f2 100644
--- a/lib/src/mirror_loader.dart
+++ b/lib/src/mirror_loader.dart
@@ -11,8 +11,8 @@ import 'package:initialize/initialize.dart';
 final _root = currentMirrorSystem().isolate.rootLibrary;
 
 Queue<Function> loadInitializers(
-    {List<Type> typeFilter, InitializerFilter customFilter}) {
-  return new InitializationCrawler(typeFilter, customFilter).run();
+    {List<Type> typeFilter, InitializerFilter customFilter, Uri from}) {
+  return new InitializationCrawler(typeFilter, customFilter, from: from).run();
 }
 
 // Crawls a library and all its dependencies for `Initializer` annotations using
@@ -30,7 +30,19 @@ class InitializationCrawler {
   // function will be processed.
   final InitializerFilter customFilter;
 
-  InitializationCrawler(this.typeFilter, this.customFilter);
+  /// Optional property, if supplied then crawling will run from this library
+  /// only.
+  ///
+  /// Note: This is only supported in the mirror_loader.dart. It is not
+  /// supported statically.
+  final LibraryMirror _rootLibrary;
+
+  InitializationCrawler(this.typeFilter, this.customFilter, {Uri from})
+      : _rootLibrary = currentMirrorSystem().libraries[from] {
+    if (from != null && _rootLibrary == null) {
+      throw 'Unable to find library at $from.';
+    }
+  }
 
   // The primary function in this class, invoke it to crawl and collect all the
   // annotations into a queue of init functions.
@@ -39,8 +51,9 @@ class InitializationCrawler {
     var queue = new Queue<Function>();
     var libraries = currentMirrorSystem().libraries;
 
-    var trampolineUri = Uri.parse('${_root.uri}\$trampoline');
-    if (libraries.containsKey(trampolineUri)) {
+    if (_rootLibrary != null) {
+      _readLibraryDeclarations(_rootLibrary, librariesSeen, queue);
+    } else if (libraries.containsKey(Uri.parse('${_root.uri}\$trampoline'))) {
       // In dartium, process all relative libraries in reverse order of when
       // they were seen.
       // TODO(jakemac): This is an approximation of what we actually want.