fixes #52, fields shadowing getters/setters or other fields

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 ff74032313e2feab347aae6729c9674ba3707a1d..4bc40565d1ff7cab881bbe3641116568179cc094 100644
--- a/lib/runtime/dart/isolate.js
+++ b/lib/runtime/dart/isolate.js
@@ -8,7 +8,7 @@ var isolate;
   }
   class IsolateSpawnException extends core.Object {
     IsolateSpawnException(message) {
-      this.message = message;
+      dart.initField(IsolateSpawnException, this, 'message', message);
     }
     toString() {
       return `IsolateSpawnException: ${this.message}`;
@@ -21,9 +21,9 @@ var isolate;
     Isolate(controlPort, opts) {
       let pauseCapability = opts && 'pauseCapability' in opts ? opts.pauseCapability : null;
       let terminateCapability = opts && 'terminateCapability' in opts ? opts.terminateCapability : null;
-      this.controlPort = controlPort;
-      this.pauseCapability = pauseCapability;
-      this.terminateCapability = terminateCapability;
+      dart.initField(Isolate, this, 'controlPort', controlPort);
+      dart.initField(Isolate, this, 'pauseCapability', pauseCapability);
+      dart.initField(Isolate, this, 'terminateCapability', terminateCapability);
     }
     static get current() {
       return Isolate[_currentIsolateCache];
@@ -192,8 +192,8 @@ var isolate;
   let _description = Symbol('_description');
   class RemoteError extends core.Object {
     RemoteError(description, stackDescription) {
-      this[_description] = description;
-      this.stackTrace = new _RemoteStackTrace(stackDescription);
+      dart.initField(RemoteError, this, _description, description);
+      dart.initField(RemoteError, this, 'stackTrace', new _RemoteStackTrace(stackDescription));
     }
     toString() {
       return this[_description];