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

base/memory/shared_memory_handle.h

Index: base/memory/shared_memory_handle.h
diff --git a/base/memory/shared_memory_handle.h b/base/memory/shared_memory_handle.h
index dc33eeafa11faef22f73be0d44dd30447e43118b..3834d868128c6f3cfdd24f6153d832975d2be1ef 100644
--- a/base/memory/shared_memory_handle.h
+++ b/base/memory/shared_memory_handle.h
@@ -152,6 +152,8 @@ class BASE_EXPORT SharedMemoryHandle {
   void SetOwnershipPassesToIPC(bool ownership_passes);
   bool OwnershipPassesToIPC() const;
 
+  bool GetUniqueID(SharedMemoryHandleID* id) const;
+
  private:
   friend class SharedMemory;
 
@@ -186,6 +188,43 @@ class BASE_EXPORT SharedMemoryHandle {
 };
 #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_