Address Ivan's review comments.

runtime/lib/date.cc

 // 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.
 
 #include "vm/bootstrap_natives.h"
 
 #include "vm/bigint_operations.h"
-#include "vm/exceptions.h"
 #include "vm/native_entry.h"
 #include "vm/object.h"
 #include "vm/os.h"
 
 namespace dart {
 
 static bool BreakDownSecondsSinceEpoch(const Integer& dart_seconds,
                                        const Bool& dart_is_utc,
                                        OS::BrokenDownDate* result) {
   bool is_utc = dart_is_utc.value();
@@ skipping 128 matching lines @@
   bool succeeded =
       BreakDownSecondsSinceEpoch(dart_seconds, dart_is_utc, &broken_down);
   if (!succeeded) {
     UNIMPLEMENTED();
   }
   const Smi& result = Smi::Handle(Smi::New(broken_down.seconds));
   arguments->SetReturn(result);
 }
 
 }  // namespace dart