Update Future tests to match new "stackTrace" property.

tests/corelib/future_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 // Tests for Future.immediate
 
 testImmediate() {
   final future = new Future<String>.immediate("42");
   Expect.isTrue(future.isComplete);
   Expect.isTrue(future.hasValue);
@@ skipping 290 matching lines @@
   future.handleException((e) { ex2 = e; return false; });
   Expect.throws(() { future.then((e) { }); });
   Expect.equals(ex, ex2);
 }
 
 // Tests for accessing the exception call stack.
 
 testCallStackThrowsIfNotComplete() {
   var exception;
   try {
-    new Completer().future.callStack;
+    new Completer().future.stackTrace;
   } catch (var ex) {
     exception = ex;
   }
 
   Expect.isTrue(exception is FutureNotCompleteException);
 }
 
 testCallStackIsNullIfCompletedSuccessfully() {
-  Expect.isNull(new Future.immediate('blah').callStack);
+  Expect.isNull(new Future.immediate('blah').stackTrace);
 }
 
 testCallStackReturnsCallstackPassedToCompleteException() {
   final completer = new Completer();
   final future = completer.future;
 
-  final callstack = 'fake call stack';
-  completer.completeException(new Exception(), callstack);
-  Expect.equals(callstack, future.callStack);
+  final stackTrace = 'fake stack trace';
+  completer.completeException(new Exception(), stackTrace);
+  Expect.equals(stackTrace, future.stackTrace);
 }
 
 testCallStackIsCapturedIfTransformCallbackThrows() {
   final completer = new Completer();
   final transformed = completer.future.transform((_) {
     throw 'whoops!';
   });
 
-  final callstack = 'fake call stack';
+  final stackTrace = 'fake stack trace';
   completer.complete('blah');
-  Expect.isNotNull(transformed.callStack);
+  Expect.isNotNull(transformed.stackTrace);
 }
 
 testCallStackIsCapturedIfChainCallbackThrows() {
   final completer = new Completer();
   final chained = completer.future.chain((_) {
     throw 'whoops!';
   });
 
-  final callstack = 'fake call stack';
+  final stackTrace = 'fake stack trace';
   completer.complete('blah');
-  Expect.isNotNull(chained.callStack);
+  Expect.isNotNull(chained.stackTrace);
 }
 
 // Tests for mixed usage of [onComplete], [then], and [handleException]
 
 testCompleteWithCompletionAndSuccessHandlers() {
   final completer = new Completer<int>();
   final future = completer.future;
 
   var valueFromSuccessHandler;
   var valueFromCompletionHandler;
@@ skipping 165 matching lines @@
   testExceptionWithCompletionAndSuccessHandlers();
   testExceptionWithCompletionAndSuccessAndExceptionHandlers();
   testTransformSuccess();
   testTransformFutureFails();
   testTransformTransformerFails();
   testChainSuccess();
   testChainFirstFutureFails();
   testChainTransformerFails();
   testChainSecondFutureFails();
 }