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

base/memory/shared_memory.h

Index: base/memory/shared_memory.h
diff --git a/base/memory/shared_memory.h b/base/memory/shared_memory.h
index d3daa80717432d6ec40ec1841f7a73ff7f0f1569..34cdc1ed16273befbaa8258f01777b95af33efaf 100644
--- a/base/memory/shared_memory.h
+++ b/base/memory/shared_memory.h
@@ -92,17 +92,15 @@ class BASE_EXPORT SharedMemory {
   // 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)