make base::SharedMemoryHandle a class on POSIX.

base/memory/shared_memory_unittest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/memory/shared_memory.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <memory>
@@ skipping 203 matching lines @@
 
   SharedMemory memory;
   ASSERT_TRUE(memory.CreateAndMapAnonymous(kDataSize));
   char* ptr = static_cast<char*>(memory.memory());
   ASSERT_NE(ptr, static_cast<void*>(NULL));
   memset(ptr, 'G', kDataSize);
 
   memory.Close();
 
   EXPECT_EQ(ptr, memory.memory());
-  EXPECT_EQ(SharedMemory::NULLHandle(), memory.handle());
+  EXPECT_TRUE(!memory.handle().IsValid());
 
   for (size_t i = 0; i < kDataSize; i++) {
     EXPECT_EQ('G', ptr[i]);
   }
 
   memory.Unmap();
   EXPECT_EQ(nullptr, memory.memory());
 }
 
 #if !defined(OS_MACOSX)
@@ skipping 466 matching lines @@
   memory.Close();
   SharedMemoryProcessTest::CleanUp();
 }
 
 MULTIPROCESS_TEST_MAIN(SharedMemoryTestMain) {
   return SharedMemoryProcessTest::TaskTestMain();
 }
 #endif  // !defined(OS_IOS) && !defined(OS_ANDROID) && !defined(OS_MACOSX)
 
 }  // namespace base