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

base/memory/shared_memory_handle.h

 // 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.
 
 #ifndef BASE_MEMORY_SHARED_MEMORY_HANDLE_H_
 #define BASE_MEMORY_SHARED_MEMORY_HANDLE_H_
 
 #include <stddef.h>
 
 #include "build/build_config.h"
@@ skipping 134 matching lines @@
   // On success, |memory| is an output variable that contains the start of the
   // mapped memory.
   bool MapAt(off_t offset, size_t bytes, void** memory, bool read_only);
 
   // Closes the underlying OS primitive.
   void Close() const;
 
   void SetOwnershipPassesToIPC(bool ownership_passes);
   bool OwnershipPassesToIPC() const;
 
+  bool GetUniqueID(SharedMemoryHandleID* id) const;
+
  private:
   friend class SharedMemory;
 
   // Shared code between copy constructor and operator=.
   void CopyRelevantData(const SharedMemoryHandle& handle);
 
   Type type_;
 
   // Each instance of a SharedMemoryHandle is backed either by a POSIX fd or a
   // mach port. |type_| determines the backing member.
@@ skipping 14 matching lines @@
       // Whether passing this object as a parameter to an IPC message passes
       // ownership of |memory_object_| to the IPC stack. This is meant to mimic
       // the behavior of the |auto_close| parameter of FileDescriptor.
       // Defaults to |false|.
       bool ownership_passes_to_ipc_;
     };
   };
 };
 #endif
 
+#if defined(OS_POSIX) && !(defined(OS_MACOSX) && !defined(OS_IOS))
+struct SharedMemoryHandleID {
+  dev_t device_id;
+  ino_t file_id;
+};
+#elif defined(OS_MACOSX)
+struct SharedMemoryHandleID {
+  // TODO: On macOS, this might be mach_port_t.
+  dev_t device_id;
+  ino_t file_id;
+};
+#elif defined(OS_WIN)
+struct SharedMemoryHandleID {
+  DWORD device_id;   // BY_HANDLE_FILE_INFORMATION.dwVolumeSerialNumber
+  intt64_t file_id;  // BY_HANDLE_FILE_INFORMATION.nFileIndexHigh and Low
+};
+#endif
+
+bool GetIDFromSharedMemoryHandle(const SharedMemoryHandle& handle,
+                                 SharedMemoryHandleID* id);
+
+std::string GetSharedMemoryHandleIDString(const SharedMemoryHandleID& id);
+
+struct SharedMemoryHandleIDHash {
+  std::size_t operator()(const SharedMemoryHandleID& id) const {
+    return std::hash<int64_t>()(static_cast<int64_t>(id.device_id)) ^
+           std::hash<int64_t>()(static_cast<int64_t>(id.file_id));
+  }
+};
+
+struct SharedMemoryHandleIDEqual {
+  bool operator()(const SharedMemoryHandleID& lhs,
+                  const SharedMemoryHandleID& rhs) const {
+    return lhs.device_id == rhs.device_id && lhs.file_id == rhs.file_id;
+  }
+};
+
 }  // namespace base
 
 #endif  // BASE_MEMORY_SHARED_MEMORY_HANDLE_H_