- Make size of the stack red zone depend on word size.

runtime/vm/isolate.h

 // Copyright (c) 2013, 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_ISOLATE_H_
 #define VM_ISOLATE_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/thread.h"
@@ skipping 186 matching lines @@
 
   // The current stack limit.  This may be overwritten with a special
   // value to trigger interrupts.
   uword stack_limit() const { return stack_limit_; }
 
   // The true stack limit for this isolate.
   uword saved_stack_limit() const { return saved_stack_limit_; }
 
   static uword GetSpecifiedStackSize();
 
-  static const intptr_t kStackSizeBuffer = (16 * KB);
+  static const intptr_t kStackSizeBuffer = (4 * KB * kWordSize);
 
   enum {
     kApiInterrupt = 0x1,      // An interrupt from Dart_InterruptIsolate.
     kMessageInterrupt = 0x2,  // An interrupt to process an out of band message.
     kStoreBufferInterrupt = 0x4,  // An interrupt to process the store buffer.
 
     kInterruptsMask =
         kApiInterrupt |
         kMessageInterrupt |
         kStoreBufferInterrupt,
@@ skipping 242 matching lines @@
   Isolate* new_isolate_;
   Isolate* saved_isolate_;
   uword saved_stack_limit_;
 
   DISALLOW_COPY_AND_ASSIGN(SwitchIsolateScope);
 };
 
 }  // namespace dart
 
 #endif  // VM_ISOLATE_H_