unittest step 3 and 4: remove TestFramework.dart, make test.dart use

samples/tests/samples/src/proxy/MintMakerRpcTest.dart

Index: samples/tests/samples/src/proxy/MintMakerRpcTest.dart
diff --git a/samples/tests/samples/src/proxy/MintMakerRpcTest.dart b/samples/tests/samples/src/proxy/MintMakerRpcTest.dart
index baa04022ce780f0ef5f5636acf781d3597829efb..d717b78127acecc314fdca7a48c9b47425baa4d6 100644
--- a/samples/tests/samples/src/proxy/MintMakerRpcTest.dart
+++ b/samples/tests/samples/src/proxy/MintMakerRpcTest.dart
@@ -173,7 +173,9 @@ class MintIsolate extends Isolate {
   }
 
   void main() {
-    ReceivePort receivePort = port;
+    // Note: 'super.' is needed here because the isolate library also defines a
+    // top-level port, and that port is resolved first.
+    ReceivePort receivePort = super.port;
     new MintReceiver(receivePort);
   }
 }