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..18eb2558d23c95661af0102d2aac22aa88baa040 100644
--- a/net/disk_cache/disk_cache.h
+++ b/net/disk_cache/disk_cache.h
@@ -25,6 +25,9 @@
 namespace base {
 class FilePath;
 class SingleThreadTaskRunner;
+namespace trace_event {
+class ProcessMemoryDump;
+}
 }
 
 namespace net {
@@ -174,6 +177,13 @@ 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;
+
+  // Dumps memory allocation stats. |parent_dump_absolute_name| is the name
+  // used by the parent MemoryAllocatorDump in the memory dump hierarchy.
+  // TODO(xunjieli): Investigate memory usage from backends other than
+  // SimpleCache.

[ssid, 2017/02/01 02:45:48]

Slightly weird place to have this TODO about implementation at the interface. I
would suggest making this pure virtual and having TODO in the actual classes.

[xunjieli, 2017/02/01 14:55:18]

Done.

+  virtual void DumpMemoryStats(base::trace_event::ProcessMemoryDump* pmd,
+                               const std::string& parent_absolute_name) const {}
 };
 
 // This interface represents an entry in the disk cache.