Track SimpleCache memory usage in net/ MemoryDumpProvider

net/disk_cache/disk_cache.h

Index: net/disk_cache/disk_cache.h
diff --git a/net/disk_cache/disk_cache.h b/net/disk_cache/disk_cache.h
index 09924065c4b7bc39be9b031246e9456a0042b888..a2001c8b8fd00909f7d5239c9bab027da2cf4739 100644
--- a/net/disk_cache/disk_cache.h
+++ b/net/disk_cache/disk_cache.h
@@ -174,6 +174,9 @@ class NET_EXPORT Backend {
   // Called whenever an external cache in the system reuses the resource
   // referred to by |key|.
   virtual void OnExternalCacheHit(const std::string& key) = 0;
+
+  // Returns the estimate of dynamically allocated memory in bytes.
+  virtual size_t EstimateMemoryUsage() const = 0;
 };
 
 // This interface represents an entry in the disk cache.