Merge the dart:uri library into dart:core and update the Uri class

sdk/lib/_internal/compiler/implementation/compiler.dart

Index: sdk/lib/_internal/compiler/implementation/compiler.dart
diff --git a/sdk/lib/_internal/compiler/implementation/compiler.dart b/sdk/lib/_internal/compiler/implementation/compiler.dart
index 5afc41de52b0917dd90914622c35f5616d25a993..f14543f3dcae2b23c108967dfbc57f81277b579e 100644
--- a/sdk/lib/_internal/compiler/implementation/compiler.dart
+++ b/sdk/lib/_internal/compiler/implementation/compiler.dart
@@ -744,7 +744,7 @@ abstract class Compiler implements DiagnosticListener {
     invokeOnMethod = jsInvocationMirrorClass.lookupLocalMember(INVOKE_ON);
 
     if (preserveComments) {
-      var uri = new Uri.fromComponents(scheme: 'dart', path: 'mirrors');
+      var uri = new Uri(scheme: 'dart', path: 'mirrors');
       LibraryElement libraryElement =
           libraryLoader.loadLibrary(uri, null, uri);
       documentClass = libraryElement.find(const SourceString('Comment'));