Replace SharedMemory::UniqueID usages with SharedMemoryHandle's guid

base/memory/shared_memory_tracker.h

Index: base/memory/shared_memory_tracker.h
diff --git a/base/memory/shared_memory_tracker.h b/base/memory/shared_memory_tracker.h
index 039e48d515fafc1fe2b49bcee9f743d485de3454..bb95214cab16e4b4570c4a270c7c317fe9debc9a 100644
--- a/base/memory/shared_memory_tracker.h
+++ b/base/memory/shared_memory_tracker.h
@@ -31,14 +31,6 @@ class BASE_EXPORT SharedMemoryTracker
   void DecrementMemoryUsage(const SharedMemory& shared_memory);
 
  private:
-  struct Usage {
-    Usage();
-    Usage(const Usage& rhs);
-    ~Usage();
-    SharedMemory::UniqueId unique_id;
-    size_t size;
-  };
-
   SharedMemoryTracker();
   ~SharedMemoryTracker() override;
 
@@ -48,7 +40,7 @@ class BASE_EXPORT SharedMemoryTracker
 
   // Used to lock when |usages_| is modified or read.
   Lock usages_lock_;
-  std::unordered_map<const SharedMemory*, Usage> usages_;
+  std::unordered_map<const SharedMemory*, size_t> usages_;
 
   DISALLOW_COPY_AND_ASSIGN(SharedMemoryTracker);
 };