[HttpCache] Store some memcache info to memory dumps for debugging

net/disk_cache/memory/mem_backend_impl.h

Index: net/disk_cache/memory/mem_backend_impl.h
diff --git a/net/disk_cache/memory/mem_backend_impl.h b/net/disk_cache/memory/mem_backend_impl.h
index be4c08ff386280ef034576ba1c9c9ec21bfcd94d..44937a0d54fe2eb1711a5d7d5232991916203b7e 100644
--- a/net/disk_cache/memory/mem_backend_impl.h
+++ b/net/disk_cache/memory/mem_backend_impl.h
@@ -98,7 +98,9 @@ class NET_EXPORT_PRIVATE MemBackendImpl final : public Backend {
   std::unique_ptr<Iterator> CreateIterator() override;
   void GetStats(base::StringPairs* stats) override {}
   void OnExternalCacheHit(const std::string& key) override;
-  size_t EstimateMemoryUsage() const override;
+  size_t DumpMemoryStats(
+      base::trace_event::ProcessMemoryDump* pmd,
+      const std::string& parent_absolute_name) const override;
 
  private:
   class MemIterator;