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

net/disk_cache/blockfile/backend_impl.cc

Index: net/disk_cache/blockfile/backend_impl.cc
diff --git a/net/disk_cache/blockfile/backend_impl.cc b/net/disk_cache/blockfile/backend_impl.cc
index cde4b701ae2eefd1e819b9f9373bfae4059e54e1..4557531fc273f3a723cfbcc7f56d289327fe0a67 100644
--- a/net/disk_cache/blockfile/backend_impl.cc
+++ b/net/disk_cache/blockfile/backend_impl.cc
@@ -26,6 +26,7 @@
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/time/time.h"
 #include "base/timer/timer.h"
+#include "base/trace_event/process_memory_dump.h"
 #include "net/base/net_errors.h"
 #include "net/disk_cache/blockfile/disk_format.h"
 #include "net/disk_cache/blockfile/entry_impl.h"
@@ -1320,9 +1321,11 @@ void BackendImpl::OnExternalCacheHit(const std::string& key) {
   background_queue_.OnExternalCacheHit(key);
 }
 
-size_t BackendImpl::EstimateMemoryUsage() const {
+size_t BackendImpl::DumpMemoryStats(
+    base::trace_event::ProcessMemoryDump* pmd,
+    const std::string& parent_absolute_name) const {
   // TODO(xunjieli): Implement this. crbug.com/669108.
-  return 0;
+  return 0u;
 }
 
 // ------------------------------------------------------------------------