Revert of Revert of Make SharedMemoryHandle a class on Mac.

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 68db65c2f3221c9419de0b86ae6f6469d9bb18d1..4326758177aac577f3f1f6702c027b19b25ff665 100644
--- a/base/memory/shared_memory.h
+++ b/base/memory/shared_memory.h
@@ -17,6 +17,7 @@
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
+#include "base/memory/shared_memory_handle.h"
 #include "base/process/process_handle.h"
 
 #if defined(OS_POSIX)
@@ -28,14 +29,6 @@
 namespace base {
 
 class FilePath;
-
-// SharedMemoryHandle is a platform specific type which represents
-// the underlying OS handle to a shared memory segment.
-#if defined(OS_WIN)
-typedef HANDLE SharedMemoryHandle;
-#elif defined(OS_POSIX)
-typedef FileDescriptor SharedMemoryHandle;
-#endif
 
 // Options for creating a shared memory object.
 struct SharedMemoryCreateOptions {
@@ -89,12 +82,13 @@
   // only affects how the SharedMemory will be mmapped.  Use
   // ShareReadOnlyToProcess to drop permissions.  TODO(jln,jyasskin): DCHECK
   // that |read_only| matches the permissions of the handle.
-  SharedMemory(SharedMemoryHandle handle, bool read_only);
+  SharedMemory(const SharedMemoryHandle& handle, bool read_only);
 
   // Create a new SharedMemory object from an existing, open
   // shared memory file that was created by a remote process and not shared
   // to the current process.
-  SharedMemory(SharedMemoryHandle handle, bool read_only,
+  SharedMemory(const SharedMemoryHandle& handle,
+               bool read_only,
                ProcessHandle process);
 
   // Closes any open files.