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

runtime/vm/os.h

 // Copyright (c) 2011, 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.
 
 #ifndef VM_OS_H_
 #define VM_OS_H_
 
 #include "vm/globals.h"
 
 // Forward declarations.
@@ skipping 42 matching lines @@
     return result;
   }
 
   // Returns an aligned pointer in the C heap with room for size bytes.
   // Alignment must be >= 16 and a power of two.
   static void* AlignedAllocate(intptr_t size, intptr_t alignment);
 
   // Frees a pointer returned from AlignedAllocate.
   static void AlignedFree(void* ptr);
 
-  // Returns the activation frame alignment constraint or zero if
+  // Returns the activation frame alignment constraint or one if
   // the platform doesn't care. Guaranteed to be a power of two.
   static word ActivationFrameAlignment();
 
   // This constant is guaranteed to be greater or equal to the
   // preferred code alignment on all platforms.
   static const int kMaxPreferredCodeAlignment = 32;
 
   // Returns the preferred code alignment or zero if
   // the platform doesn't care. Guaranteed to be a power of two.
   static word PreferredCodeAlignment();
@@ skipping 57 matching lines @@
   static void Shutdown();
 
   static void Abort();
 
   static void Exit(int code);
 };
 
 }  // namespace dart
 
 #endif  // VM_OS_H_