Track SimpleCache memory usage in net/ MemoryDumpProvider

net/disk_cache/simple/simple_backend_impl.h

Index: net/disk_cache/simple/simple_backend_impl.h
diff --git a/net/disk_cache/simple/simple_backend_impl.h b/net/disk_cache/simple/simple_backend_impl.h
index a0b4b9c42820e8b05f6dcd3639e5a534af077424..028060f975d2e483e3b32c4ba899a8833a93c04a 100644
--- a/net/disk_cache/simple/simple_backend_impl.h
+++ b/net/disk_cache/simple/simple_backend_impl.h
@@ -31,6 +31,9 @@
 namespace base {
 class SingleThreadTaskRunner;
 class TaskRunner;
+namespace trace_event {
+class ProcessMemoryDump;
+}
 }
 
 namespace disk_cache {
@@ -117,6 +120,8 @@ class NET_EXPORT_PRIVATE SimpleBackendImpl : public Backend,
   std::unique_ptr<Iterator> CreateIterator() override;
   void GetStats(base::StringPairs* stats) override;
   void OnExternalCacheHit(const std::string& key) override;
+  void DumpMemoryStats(base::trace_event::ProcessMemoryDump* pmd,
+                       const std::string& parent_absolute_name) const override;

[ssid, 2017/01/31 22:24:19]

Do we have stats about how often we use the blockfile or mem_backend
implementation of the Backend? Is it the case that most of the time we use
SimpleCache and most of the memory usage is from EntryMetaData and we would not
have to care about the others? If not, we should make this pure and add TODO in
the classes that says implement this later.

[xunjieli, 2017/02/01 01:15:52]

We are moving towards using SimpleCache everywhere.  It's currently being used
on Android and Linux by default.  That's what show up in traces that I obtained
from Linux and Android. I don't think we care about the others, but I will add a
TODO to investigate.

 
  private:
   class SimpleIterator;