[tracing] Add a memory dump provider for DOM storage

content/browser/dom_storage/dom_storage_namespace.cc

Index: content/browser/dom_storage/dom_storage_namespace.cc
diff --git a/content/browser/dom_storage/dom_storage_namespace.cc b/content/browser/dom_storage/dom_storage_namespace.cc
index a8681b6e6c2b148491689f6c47b543172dbab08d..fa31abc8a961e0cb2bd79069c37420827cb0913c 100644
--- a/content/browser/dom_storage/dom_storage_namespace.cc
+++ b/content/browser/dom_storage/dom_storage_namespace.cc
@@ -7,6 +7,7 @@
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/logging.h"
+#include "base/trace_event/memory_dump_manager.h"
 #include "content/browser/dom_storage/dom_storage_area.h"
 #include "content/browser/dom_storage/dom_storage_task_runner.h"
 #include "content/browser/dom_storage/session_storage_database.h"
@@ -32,9 +33,16 @@ DOMStorageNamespace::DOMStorageNamespace(
       task_runner_(task_runner),
       session_storage_database_(session_storage_database) {
   DCHECK_NE(kLocalStorageNamespaceId, namespace_id);
+  base::trace_event::MemoryDumpManager::GetInstance()
+      ->RegisterDumpProviderWithSequencedTaskRunner(
+          this, "DOMStorage", task_runner_->GetSequencedTaskRunner(
+                                  DOMStorageTaskRunner::PRIMARY_SEQUENCE),
+          base::trace_event::MemoryDumpProvider::Options());
 }
 
 DOMStorageNamespace::~DOMStorageNamespace() {
+  base::trace_event::MemoryDumpManager::GetInstance()->UnregisterDumpProvider(
+      this);
 }
 
 DOMStorageArea* DOMStorageNamespace::OpenStorageArea(const GURL& origin) {
@@ -176,6 +184,15 @@ unsigned int DOMStorageNamespace::CountInMemoryAreas() const {
   return area_count;
 }
 
+bool DOMStorageNamespace::OnMemoryDump(
+    const base::trace_event::MemoryDumpArgs& args,
+    base::trace_event::ProcessMemoryDump* pmd) {
+  DCHECK(task_runner_->IsRunningOnPrimarySequence());
+  for (const auto& it : areas_)
+    it.second.area_->OnMemoryDump(pmd);
+  return true;
+}
+
 DOMStorageNamespace::AreaHolder*
 DOMStorageNamespace::GetAreaHolder(const GURL& origin) {
   AreaMap::iterator found = areas_.find(origin);