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

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 c4b4cdb64430d6fd4869711b3a000c8b8dcf7e8f..07bd44ea7a438f00c01e3badfe08b1513bbe755c 100644
--- a/base/memory/shared_memory.h
+++ b/base/memory/shared_memory.h
@@ -127,6 +127,9 @@ class BASE_EXPORT SharedMemory {
   static int GetFdFromSharedMemoryHandle(const SharedMemoryHandle& handle);
 #endif
 
+  int importance() const { return importance_; }
+  void set_importance(int importance) { importance_ = importance; }
+
   // Creates a shared memory object as described by the options struct.
   // Returns true on success and false on failure.
   bool Create(const SharedMemoryCreateOptions& options);
@@ -226,21 +229,6 @@ class BASE_EXPORT SharedMemory {
   // failure.
   SharedMemoryHandle GetReadOnlyHandle();
 
-#if defined(OS_POSIX) && (!defined(OS_MACOSX) || defined(OS_IOS)) && \
-    !defined(OS_NACL)
-  using UniqueId = std::pair<dev_t, ino_t>;
-
-  struct UniqueIdHash {
-    size_t operator()(const UniqueId& 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(UniqueId* id) const;
-#endif
-
   // Returns the last error encountered as a result of a call to Create() or
   // Map(). Note: Currently only errors from Mac POSIX shared memory
   // implementation are fully instrumented.
@@ -279,6 +267,7 @@ class BASE_EXPORT SharedMemory {
   bool read_only_ = false;
   size_t requested_size_ = 0;
   SharedMemoryError last_error_ = SharedMemoryError::NO_ERRORS;
+  int importance_ = 0;
 
   DISALLOW_COPY_AND_ASSIGN(SharedMemory);
 };