Replace SharedMemory::UniqueID usages with SharedMemoryHandle's guid

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 35067e6aaeab848080c681fa729f7853df720f3c..f0234f44faba666a8316431d789c97073c443b91 100644
--- a/base/memory/shared_memory.h
+++ b/base/memory/shared_memory.h
@@ -217,20 +217,9 @@ 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
+  // Uniques identifies the shared memory region that the underlying OS resource
+  // points to. This just returns its handler's GUID.
+  base::UnguessableToken GetGUID() const;
 
  private:
 #if defined(OS_POSIX) && !defined(OS_NACL) && !defined(OS_ANDROID) && \