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

net/disk_cache/simple/simple_backend_impl.cc

Index: net/disk_cache/simple/simple_backend_impl.cc
diff --git a/net/disk_cache/simple/simple_backend_impl.cc b/net/disk_cache/simple/simple_backend_impl.cc
index e81877c9017bef6324ef7883b2daa1357ca74456..88d2741e9797f8452efeea09fa1bbd376ed9354b 100644
--- a/net/disk_cache/simple/simple_backend_impl.cc
+++ b/net/disk_cache/simple/simple_backend_impl.cc
@@ -31,6 +31,7 @@
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/time/time.h"
 #include "base/trace_event/memory_usage_estimator.h"
+#include "base/trace_event/process_memory_dump.h"
 #include "net/base/net_errors.h"
 #include "net/disk_cache/cache_util.h"
 #include "net/disk_cache/simple/simple_entry_format.h"
@@ -560,11 +561,19 @@ void SimpleBackendImpl::OnExternalCacheHit(const std::string& key) {
   index_->UseIfExists(simple_util::GetEntryHashKey(key));
 }
 
-size_t SimpleBackendImpl::EstimateMemoryUsage() const {
+size_t SimpleBackendImpl::DumpMemoryStats(
+    base::trace_event::ProcessMemoryDump* pmd,
+    const std::string& parent_absolute_name) const {
+  base::trace_event::MemoryAllocatorDump* dump =
+      pmd->CreateAllocatorDump(parent_absolute_name + "/simple_backend");
+
+  size_t size = base::trace_event::EstimateMemoryUsage(index_) +
+                base::trace_event::EstimateMemoryUsage(active_entries_);
   // TODO(xunjieli): crbug.com/669108. Track |entries_pending_doom_| once
   // base::Closure is suppported in memory_usage_estimator.h.
-  return base::trace_event::EstimateMemoryUsage(index_) +
-         base::trace_event::EstimateMemoryUsage(active_entries_);
+  dump->AddScalar(base::trace_event::MemoryAllocatorDump::kNameSize,
+                  base::trace_event::MemoryAllocatorDump::kUnitsBytes, size);
+  return size;
 }
 
 void SimpleBackendImpl::InitializeIndex(const CompletionCallback& callback,