Fix a compiler bug caused by Utils::IsPowerOfTwo treating zero as a power of two.

runtime/platform/utils.h

 // 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.
 
 #ifndef PLATFORM_UTILS_H_
 #define PLATFORM_UTILS_H_
 
 #include "platform/assert.h"
 #include "platform/globals.h"
 
@@ skipping 12 matching lines @@
   }
 
   template<typename T>
   static inline T Abs(T x) {
     if (x < 0) return -x;
     return x;
   }
 
   template<typename T>
   static inline bool IsPowerOfTwo(T x) {
-    return (x & (x - 1)) == 0;
+    return ((x & (x - 1)) == 0) && (x != 0);
   }
 
   template<typename T>
   static inline int ShiftForPowerOfTwo(T x) {
     ASSERT(IsPowerOfTwo(x));
     int num_shifts = 0;
     while (x > 1) {
       num_shifts++;
       x = x >> 1;
     }
@@ skipping 145 matching lines @@
 #include "platform/utils_linux.h"
 #elif defined(TARGET_OS_MACOS)
 #include "platform/utils_macos.h"
 #elif defined(TARGET_OS_WINDOWS)
 #include "platform/utils_win.h"
 #else
 #error Unknown target os.
 #endif
 
 #endif  // PLATFORM_UTILS_H_