Get rid of base::SharedMemory::NULLHandle();

base/memory/shared_memory.h

 // 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.
 
 #ifndef BASE_MEMORY_SHARED_MEMORY_H_
 #define BASE_MEMORY_SHARED_MEMORY_H_
 
 #include <stddef.h>
 
 #include <string>
@@ skipping 73 matching lines @@
   // that |read_only| matches the permissions of the handle.
   SharedMemory(const SharedMemoryHandle& handle, bool read_only);
 
   // Closes any open files.
   ~SharedMemory();
 
   // Return true iff the given handle is valid (i.e. not the distingished
   // invalid value; NULL for a HANDLE and -1 for a file descriptor)
   static bool IsHandleValid(const SharedMemoryHandle& handle);
 
-  // Returns invalid handle (see comment above for exact definition).
-  static SharedMemoryHandle NULLHandle();
-
   // Closes a shared memory handle.
   static void CloseHandle(const SharedMemoryHandle& handle);
 
   // Returns the maximum number of handles that can be open at once per process.
   static size_t GetHandleLimit();
 
-  // Duplicates The underlying OS primitive. Returns NULLHandle() on failure.
-  // The caller is responsible for destroying the duplicated OS primitive.
+  // Duplicates The underlying OS primitive. Returns an invalid handle on
+  // failure. The caller is responsible for destroying the duplicated OS
+  // primitive.
   static SharedMemoryHandle DuplicateHandle(const SharedMemoryHandle& handle);
 
 #if defined(OS_POSIX)
   // This method requires that the SharedMemoryHandle is backed by a POSIX fd.
   static int GetFdFromSharedMemoryHandle(const SharedMemoryHandle& handle);
 #endif
 
 #if defined(OS_POSIX) && !defined(OS_ANDROID)
   // Gets the size of the shared memory region referred to by |handle|.
   // Returns false on a failure to determine the size. On success, populates the
@@ skipping 199 matching lines @@
   void*              memory_;
   bool               read_only_;
   size_t             requested_size_;
 
   DISALLOW_COPY_AND_ASSIGN(SharedMemory);
 };
 
 }  // namespace base
 
 #endif  // BASE_MEMORY_SHARED_MEMORY_H_