Use signature inheritance when method types are unchanged

lib/runtime/dart/isolate.js

Index: lib/runtime/dart/isolate.js
diff --git a/lib/runtime/dart/isolate.js b/lib/runtime/dart/isolate.js
index 547cd41b1e12f76b281ca23ae2d1377713b0a432..3130855a00a99ffc7386490cf57f83c3aa6854b7 100644
--- a/lib/runtime/dart/isolate.js
+++ b/lib/runtime/dart/isolate.js
@@ -19,9 +19,7 @@ var async = dart.import(async);
     }
   }
   IsolateSpawnException[dart.implements] = () => [core.Exception];
-  dart.setSignature(IsolateSpawnException, {
-    methods: () => ({toString: dart.functionType(core.String, [])})
-  });
+  dart.setSignature(IsolateSpawnException, {});
   let _pause = Symbol('_pause');
   class Isolate extends core.Object {
     Isolate(controlPort, opts) {
@@ -213,9 +211,7 @@ var async = dart.import(async);
     }
   }
   _IsolateUnhandledException[dart.implements] = () => [core.Exception];
-  dart.setSignature(_IsolateUnhandledException, {
-    methods: () => ({toString: dart.functionType(core.String, [])})
-  });
+  dart.setSignature(_IsolateUnhandledException, {});
   let _description = Symbol('_description');
   class RemoteError extends core.Object {
     RemoteError(description, stackDescription) {
@@ -227,9 +223,7 @@ var async = dart.import(async);
     }
   }
   RemoteError[dart.implements] = () => [core.Error];
-  dart.setSignature(RemoteError, {
-    methods: () => ({toString: dart.functionType(core.String, [])})
-  });
+  dart.setSignature(RemoteError, {});
   let _trace = Symbol('_trace');
   class _RemoteStackTrace extends core.Object {
     _RemoteStackTrace(trace) {
@@ -240,9 +234,7 @@ var async = dart.import(async);
     }
   }
   _RemoteStackTrace[dart.implements] = () => [core.StackTrace];
-  dart.setSignature(_RemoteStackTrace, {
-    methods: () => ({toString: dart.functionType(core.String, [])})
-  });
+  dart.setSignature(_RemoteStackTrace, {});
   // Exports:
   exports.Capability = Capability;
   exports.IsolateSpawnException = IsolateSpawnException;