Add a flag controlling how verbose stack traces are.

lib/src/frontend/future_matchers.dart

Index: lib/src/frontend/future_matchers.dart
diff --git a/lib/src/frontend/future_matchers.dart b/lib/src/frontend/future_matchers.dart
index 7dc5b493148428c07bc116a15dcaf37bd08e77f3..8a38192301e3d8fd3fe036b1991f0f2811ed57ee 100644
--- a/lib/src/frontend/future_matchers.dart
+++ b/lib/src/frontend/future_matchers.dart
@@ -60,8 +60,9 @@ class _Completes extends Matcher {
       var reason = 'Expected future ${id}to complete successfully, '
           'but it failed with ${error}';
       if (trace != null) {
-        var stackTrace = terseChain(trace).toString();
-        stackTrace = '  ${stackTrace.replaceAll('\n', '\n  ')}';
+        var stackTrace = terseChain(trace,
+            verbose: Invoker.current.metadata.verboseTrace);
+        stackTrace = '  ${stackTrace.toString().replaceAll('\n', '\n  ')}';
         reason = '$reason\nStack trace:\n$stackTrace';
       }
       fail(reason);