[tracing] Add memory statistics from level db clients to tracing.

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 d0ab442238b5817b48761a8267e5858002ba420d..5dc1605bb36ed1ce81581f96d6f71dc371abaa96 100644
--- a/content/browser/dom_storage/session_storage_database.cc
+++ b/content/browser/dom_storage/session_storage_database.cc
@@ -12,6 +12,8 @@
 #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"
@@ -95,9 +97,13 @@ SessionStorageDatabase::SessionStorageDatabase(const base::FilePath& file_path)
       is_inconsistent_(false),
       invalid_db_deleted_(false),
       operation_count_(0) {
+  base::trace_event::MemoryDumpManager::GetInstance()->RegisterDumpProvider(
+      this);
 }
 
 SessionStorageDatabase::~SessionStorageDatabase() {
+  base::trace_event::MemoryDumpManager::GetInstance()->UnregisterDumpProvider(
+      this);

[Primiano Tucci (use gerrit), 2015/10/15 08:59:52]

if you unregister the RegisterDumpProvider call above must specify a task
runner. Otherwise you can unregister while dumping on another thread, which is
racy.
There is a dcheck preventing that in UnregisterDumpProvider, did you not hit
this in debug builds?

[ssid, 2015/10/15 15:22:04]

Thanks, I guess both were done in the same thread and i did not hit DCHECK.

 }
 
 void SessionStorageDatabase::ReadAreaValues(const std::string& namespace_id,
@@ -323,6 +329,31 @@ bool SessionStorageDatabase::ReadNamespacesAndOrigins(
   return true;
 }
 
+bool SessionStorageDatabase::OnMemoryDump(
+    const base::trace_event::MemoryDumpArgs& args,
+    base::trace_event::ProcessMemoryDump* pmd) {
+  if (!db_)
+    return true;
+
+  base::trace_event::MemoryAllocatorDump* dump =
+      pmd->CreateAllocatorDump("leveldb/session_storage_db");
+
+  base::AutoLock auto_lock(db_lock_);
+  std::string value;
+  uint64 size;
+  db_->GetProperty("leveldb.approximate-memory-usage", &value);

[Primiano Tucci (use gerrit), 2015/10/15 08:59:52]

shouldn't you check the return value of GetProperty?

[ssid, 2015/10/15 15:22:04]

Actually it cannot fail. added dcheck.

+  base::StringToUint64(value, &size);
+
+  dump->AddScalar(base::trace_event::MemoryAllocatorDump::kNameSize,
+                  base::trace_event::MemoryAllocatorDump::kUnitsBytes, size);
+
+  // Memory is allocated from system allocator (malloc).
+  pmd->AddSuballocation(dump->guid(),
+                        base::trace_event::MemoryDumpManager::GetInstance()
+                            ->system_allocator_pool_name());
+  return true;
+}
+
 bool SessionStorageDatabase::LazyOpen(bool create_if_needed) {
   base::AutoLock auto_lock(db_lock_);
   if (db_error_ || is_inconsistent_) {