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

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 a2001c8b8fd00909f7d5239c9bab027da2cf4739..4a3ae119b53f9c90b22f5c70379e5d4fb0f1f057 100644
--- a/net/disk_cache/disk_cache.h
+++ b/net/disk_cache/disk_cache.h
@@ -25,8 +25,13 @@
 namespace base {
 class FilePath;
 class SingleThreadTaskRunner;
+
+namespace trace_event {
+class ProcessMemoryDump;
 }
 
+}  // namespace base
+
 namespace net {
 class IOBuffer;
 class NetLog;
@@ -176,7 +181,9 @@ class NET_EXPORT Backend {
   virtual void OnExternalCacheHit(const std::string& key) = 0;
 
   // Returns the estimate of dynamically allocated memory in bytes.
-  virtual size_t EstimateMemoryUsage() const = 0;
+  virtual size_t DumpMemoryStats(
+      base::trace_event::ProcessMemoryDump* pmd,
+      const std::string& parent_absolute_name) const = 0;
 };
 
 // This interface represents an entry in the disk cache.