Follow-up fix to my change to IsPowerOfTwo: Alignment of one means no alignment, not zero.

runtime/vm/os_win.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/globals.h"
 #if defined(TARGET_OS_WINDOWS)
 
 #include "vm/os.h"
 #include "vm/vtune.h"
 
@@ skipping 118 matching lines @@
   _aligned_free(ptr);
 }
 
 
 word OS::ActivationFrameAlignment() {
 #ifdef _WIN64
   // Windows 64-bit ABI requires the stack to be 16-byte aligned.
   return 16;
 #else
   // No requirements on Win32.
-  return 0;
+  return 1;
 #endif
 }
 
 
 word OS::PreferredCodeAlignment() {
   ASSERT(32 <= OS::kMaxPreferredCodeAlignment);
   return 32;
 }
 
 
@@ skipping 161 matching lines @@
 }
 
 
 void OS::Exit(int code) {
   exit(code);
 }
 
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_WINDOWS)