Support isExternal method on MethodMirror in the Dart VM. Not really intended for public consumptio…

runtime/lib/mirrors_impl.dart

Index: runtime/lib/mirrors_impl.dart
diff --git a/runtime/lib/mirrors_impl.dart b/runtime/lib/mirrors_impl.dart
index 0c7b0bba81290769b4fa72c0bc7599125024a47b..8b099c9bcf6121a398f3b9ad32f3b87f0b4dcd17 100644
--- a/runtime/lib/mirrors_impl.dart
+++ b/runtime/lib/mirrors_impl.dart
@@ -1372,6 +1372,7 @@ class _LocalMethodMirror extends _LocalDeclarationMirror
   static const kGenerativeCtor = 5;
   static const kRedirectingCtor = 6;
   static const kFactoryCtor = 7;
+  static const kExternal = 8;
 
   // These offsets much be kept in sync with those in mirrors.h.
   bool get isAbstract =>               0 != (_kindFlags & (1 << kAbstract));
@@ -1382,6 +1383,7 @@ class _LocalMethodMirror extends _LocalDeclarationMirror
   bool get isGenerativeConstructor =>  0 != (_kindFlags & (1 << kGenerativeCtor));
   bool get isRedirectingConstructor => 0 != (_kindFlags & (1 << kRedirectingCtor));
   bool get isFactoryConstructor =>     0 != (_kindFlags & (1 << kFactoryCtor));
+  bool get isExternal =>               0 != (_kindFlags & (1 << kExternal));
 
   static const _operators = const ["%", "&", "*", "+", "-", "/", "<", "<<",
       "<=", "==", ">", ">=", ">>", "[]", "[]=", "^", "|", "~", "unary-", "~/"];