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..1151aa6c30ee835d64a498c360a40261cbc29d0e 100644
--- a/lib/runtime/dart/isolate.js
+++ b/lib/runtime/dart/isolate.js
@@ -6,24 +6,40 @@ var isolate;
       return new _isolate_helper.CapabilityImpl();
     }
   }
+  let message$ = Symbol('message');
   class IsolateSpawnException extends core.Object {
+    get message() {
+      return this[message$];
+    }
     IsolateSpawnException(message) {
-      this.message = message;
+      this[message$] = message;
     }
     toString() {
       return `IsolateSpawnException: ${this.message}`;
     }
   }
   IsolateSpawnException[dart.implements] = () => [core.Exception];
+  let controlPort$ = Symbol('controlPort');
+  let pauseCapability$ = Symbol('pauseCapability');
+  let terminateCapability$ = Symbol('terminateCapability');
   let _currentIsolateCache = Symbol('_currentIsolateCache');
   let _pause = Symbol('_pause');
   class Isolate extends core.Object {
+    get controlPort() {
+      return this[controlPort$];
+    }
+    get pauseCapability() {
+      return this[pauseCapability$];
+    }
+    get terminateCapability() {
+      return this[terminateCapability$];
+    }
     Isolate(controlPort, opts) {
       let pauseCapability = opts && 'pauseCapability' in opts ? opts.pauseCapability : null;
       let terminateCapability = opts && 'terminateCapability' in opts ? opts.terminateCapability : null;
-      this.controlPort = controlPort;
-      this.pauseCapability = pauseCapability;
-      this.terminateCapability = terminateCapability;
+      this[controlPort$] = controlPort;
+      this[pauseCapability$] = pauseCapability;
+      this[terminateCapability$] = terminateCapability;
     }
     static get current() {
       return Isolate[_currentIsolateCache];
@@ -189,11 +205,15 @@ var isolate;
     }
   }
   _IsolateUnhandledException[dart.implements] = () => [core.Exception];
+  let stackTrace = Symbol('stackTrace');
   let _description = Symbol('_description');
   class RemoteError extends core.Object {
+    get stackTrace() {
+      return this[stackTrace];
+    }
     RemoteError(description, stackDescription) {
       this[_description] = description;
-      this.stackTrace = new _RemoteStackTrace(stackDescription);
+      this[stackTrace] = new _RemoteStackTrace(stackDescription);
     }
     toString() {
       return this[_description];