[tracing] Add a memory dump provider for DOM storage

content/browser/dom_storage/session_storage_database.cc

Index: content/browser/dom_storage/session_storage_database.cc
diff --git a/content/browser/dom_storage/session_storage_database.cc b/content/browser/dom_storage/session_storage_database.cc
index ae90b0fcc669405433e00f75ad7fd0ad28216888..1b651a68c39b277c49c9db5c869bf2f4ed61e813 100644
--- a/content/browser/dom_storage/session_storage_database.cc
+++ b/content/browser/dom_storage/session_storage_database.cc
@@ -14,6 +14,8 @@
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/trace_event/memory_dump_manager.h"
+#include "base/trace_event/process_memory_dump.h"
 #include "third_party/leveldatabase/env_chromium.h"
 #include "third_party/leveldatabase/src/include/leveldb/db.h"
 #include "third_party/leveldatabase/src/include/leveldb/iterator.h"
@@ -325,6 +327,38 @@ bool SessionStorageDatabase::ReadNamespacesAndOrigins(
   return true;
 }
 
+bool SessionStorageDatabase::OnMemoryDump(
+    base::trace_event::ProcessMemoryDump* pmd) {
+  std::string db_memory_usage;
+  {
+    base::AutoLock lock(db_lock_);
+    // Return true if |db_| is null to prevent the dump provider from being
+    // disabled, since it can be created lazily.
+    if (!db_)
+      return true;
+
+    bool res =
+        db_->GetProperty("leveldb.approximate-memory-usage", &db_memory_usage);
+    DCHECK(res);
+  }
+
+  uint64_t size;
+  bool res = base::StringToUint64(db_memory_usage, &size);
+  DCHECK(res);
+
+  auto mad = pmd->CreateAllocatorDump(
+      base::StringPrintf("dom_storage/session_storage_%p", this));
+  mad->AddScalar(base::trace_event::MemoryAllocatorDump::kNameSize,
+                 base::trace_event::MemoryAllocatorDump::kUnitsBytes, size);
+
+  // Memory is allocated from system allocator (malloc).
+  const char* system_allocator_name =
+      base::trace_event::MemoryDumpManager::GetInstance()
+          ->system_allocator_pool_name();
+  if (system_allocator_name)
+    pmd->AddSuballocation(mad->guid(), system_allocator_name);
+  return true;
+}
 bool SessionStorageDatabase::LazyOpen(bool create_if_needed) {
   base::AutoLock auto_lock(db_lock_);
   if (db_error_ || is_inconsistent_) {