Fix await transformation of function calls

tests/language/await_regression_test.dart

Index: tests/language/await_regression_test.dart
diff --git a/tests/language/await_regression_test.dart b/tests/language/await_regression_test.dart
index 9c3e663471b03a8c9b8429650c47741ed91bbe41..90a562dd0a7d57a9b25ee8db91ea9c864b3aecb3 100644
--- a/tests/language/await_regression_test.dart
+++ b/tests/language/await_regression_test.dart
@@ -30,7 +30,19 @@ testNamedArguments() async {
   Expect.equals(sum, 0);
 }
 
+testSideEffects() async {
+  Future foo(int a1, int a2) {
+    Expect.equals(10, a1);
+    Expect.equals(11, a2);
+    return new Future.value();
+  }
+  int a = 10;
+  await foo(a++, a++);
+  Expect.equals(12, a);
+}
+
 main() async {
   testNestedFunctions();
   testNamedArguments();
+  testSideEffects();
 }