Remove warnings from dart2js test-suite.

sdk/lib/mirrors/mirrors.dart

Index: sdk/lib/mirrors/mirrors.dart
diff --git a/sdk/lib/mirrors/mirrors.dart b/sdk/lib/mirrors/mirrors.dart
index ddffcd67a23200f3a791912d6a797cf703b500db..7fb810e9b87d3ff865768437e9ce35f6ba18f0f5 100644
--- a/sdk/lib/mirrors/mirrors.dart
+++ b/sdk/lib/mirrors/mirrors.dart
@@ -55,9 +55,6 @@
  */
 library dart.mirrors;
 
-import 'dart:async';
-import 'dart:isolate';
-
 /**
  * A [MirrorSystem] is the main interface used to reflect on a set of
  * associated libraries.
@@ -569,7 +566,7 @@ abstract class LibraryMirror implements DeclarationMirror, ObjectMirror {
 }
 
 /// A mirror on an import or export declaration.
-abstract class LibraryDependencyMirror {
+abstract class LibraryDependencyMirror implements Mirror {
   /// Is `true` if this dependency is an import.
   bool get isImport;
 
@@ -597,7 +594,7 @@ abstract class LibraryDependencyMirror {
 }
 
 /// A mirror on a show/hide combinator declared on a library dependency.
-abstract class CombinatorMirror {
+abstract class CombinatorMirror implements Mirror {
   /// The list of identifiers on the combinator.
   List<Symbol> get identifiers;