base: Introduce SharedMemoryTracker for POSIX (but not macOS)

base/memory/shared_memory.h

 // Copyright (c) 2012 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_H_
 #define BASE_MEMORY_SHARED_MEMORY_H_
 
 #include <stddef.h>
 
 #include <string>
@@ skipping 237 matching lines @@
   //   bool ok = ShareToProcess(process, new_handle);
   //   Close();
   //   return ok;
   // Note that the memory is unmapped by calling this method, regardless of the
   // return value.
   bool GiveToProcess(ProcessHandle process,
                      SharedMemoryHandle* new_handle) {
     return ShareToProcessCommon(process, new_handle, true, SHARE_CURRENT_MODE);
   }
 
+#if defined(OS_POSIX) && (!defined(OS_MACOSX) || defined(OS_IOS)) && \
+    !defined(OS_NACL)
+  using Id = std::pair<dev_t, ino_t>;

[danakj, 2017/02/24 15:30:28]

one request, lets give this a more.. unique.. name than just "id". How about
UniqueId?

[hajimehoshi, 2017/02/27 07:51:54]

Done.

+
+  struct IdHash {
+    size_t operator()(const Id& id) const {
+      return HashInts(id.first, id.second);
+    }
+  };
+
+  // Returns a unique ID for this shared memory's handle. Note this function may
+  // access file system and be slow.
+  bool GetUniqueId(Id* id) const;
+#endif
+
  private:
 #if defined(OS_POSIX) && !defined(OS_NACL) && !defined(OS_ANDROID) && \
-    !(defined(OS_MACOSX) && !defined(OS_IOS))
+    (!defined(OS_MACOSX) || defined(OS_IOS))
   bool FilePathForMemoryName(const std::string& mem_name, FilePath* path);
 #endif
 
   enum ShareMode {
     SHARE_READONLY,
     SHARE_CURRENT_MODE,
   };
 
 #if defined(OS_MACOSX)
   bool Share(SharedMemoryHandle* new_handle, ShareMode share_mode);
@@ skipping 23 matching lines @@
   int                mapped_file_;
   int                readonly_mapped_file_;
 #endif
   size_t             mapped_size_;
   void*              memory_;
   bool               read_only_;
   size_t             requested_size_;
 
   DISALLOW_COPY_AND_ASSIGN(SharedMemory);
 };
+
 }  // namespace base
 
 #endif  // BASE_MEMORY_SHARED_MEMORY_H_