Fix warnings on Win64.

src/regexp-stack.h

 // Copyright 2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 50 matching lines @@
   // There is only a limited number of locations below the stack limit,
   // so users of the stack should check the stack limit during any
   // sequence of pushes longer that this.
   static Address* limit_address() { return &(thread_local_.limit_); }
 
   // Ensures that there is a memory area with at least the specified size.
   // If passing zero, the default/minimum size buffer is allocated.
   static Address EnsureCapacity(size_t size);
 
   // Thread local archiving.
-  static size_t ArchiveSpacePerThread() { return sizeof(thread_local_); }
+  static int ArchiveSpacePerThread() {
+    return static_cast<int>(sizeof(thread_local_));
+  }
   static char* ArchiveStack(char* to);
   static char* RestoreStack(char* from);
   static void FreeThreadResources() { thread_local_.Free(); }
 
  private:
   // Artificial limit used when no memory has been allocated.
   static const uintptr_t kMemoryTop = static_cast<uintptr_t>(-1);
 
   // Minimal size of allocated stack area.
   static const size_t kMinimumStackSize = 1 * KB;
@@ skipping 18 matching lines @@
   // After this, the buffer is either the default size, or it is empty, so
   // you have to call EnsureCapacity before using it again.
   static void Reset();
 
   static ThreadLocal thread_local_;
 };
 
 }}  // namespace v8::internal
 
 #endif  // V8_REGEXP_STACK_H_