Parse await as part of an unary expression.

tests/language/await_future_test.dart

 // Copyright (c) 2014, 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.
 
 // VMOptions=--enable_async --optimization-counter-threshold=5
 
 import 'package:expect/expect.dart';
 
 import 'dart:async';
 
@@ skipping 52 matching lines @@
       var a = await y();
       throw a;
     } catch (e2) {
       throw e2 + 1;
     }
   } catch (e3) {
     return e3;
   }
 }
 
+awaitAsUnary(a,b) async {
+  return await a + await b;
+}
+
 awaitIf(p) async {
   if (p < (await bar(5))) {
     return "p<5";
   } else {
     return "p>=5";
   }
 }
 
 awaitNestedIf(p,q) async {
   if (p == (await bar(5))) {
@@ skipping 99 matching lines @@
     result = await awaitElseIf(6);
     Expect.equals("p>5", result);
     result = await awaitElseIf(4);
     Expect.equals("p<5", result);
     result = await awaitElseIf(5);
     Expect.equals("p==5", result);
     result = await awaitNestedWhile(5,3);
     Expect.equals(15, result);
     result = await awaitNestedWhile(4,6);
     Expect.equals(24, result);
+    result = await awaitAsUnary(bar(1), bar(2));
+    Expect.equals(3, result);
   }
 }