[WIP] Add SharedMemoryTracker to dump base::SharedMemory usage

base/memory/shared_memory_handle_mac.cc

 // Copyright 2015 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_handle.h"
 
 #include <mach/mach_vm.h>
 #include <stddef.h>
 #include <sys/mman.h>
 #include <unistd.h>
@@ skipping 198 matching lines @@
       break;
     case MACH:
       memory_object_ = handle.memory_object_;
       size_ = handle.size_;
       pid_ = handle.pid_;
       ownership_passes_to_ipc_ = handle.ownership_passes_to_ipc_;
       break;
   }
 }
 
+bool GetIDFromSharedMemoryHandle(const SharedMemoryHandle& handle,
+                                 SharedMemoryHandleID* id) {
+  // TODO(hajimehoshi): Implement this.
+  return true;
+}
+
+std::string GetSharedMemoryHandleIDString(const SharedMemoryHandleID& id) {
+  // TODO(hajimehoshi): Implement this.
+  return "";
+}
+
 }  // namespace base