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

extensions/browser/value_store/leveldb_value_store.cc

Index: extensions/browser/value_store/leveldb_value_store.cc
diff --git a/extensions/browser/value_store/leveldb_value_store.cc b/extensions/browser/value_store/leveldb_value_store.cc
index 39a1346df7d2c2ca41d92585254cf4401e397436..869d714e86321924790040d3075c740f1ec4be36 100644
--- a/extensions/browser/value_store/leveldb_value_store.cc
+++ b/extensions/browser/value_store/leveldb_value_store.cc
@@ -8,9 +8,13 @@
 #include "base/json/json_reader.h"
 #include "base/json/json_writer.h"
 #include "base/logging.h"
+#include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/sys_string_conversions.h"
+#include "base/thread_task_runner_handle.h"
+#include "base/trace_event/memory_dump_manager.h"
+#include "base/trace_event/process_memory_dump.h"
 #include "content/public/browser/browser_thread.h"
 #include "extensions/browser/value_store/value_store_util.h"
 #include "third_party/leveldatabase/env_chromium.h"
@@ -59,10 +63,14 @@ LeveldbValueStore::LeveldbValueStore(const std::string& uma_client_name,
       "Extensions.Database.Open." + uma_client_name, 1,
       leveldb_env::LEVELDB_STATUS_MAX, leveldb_env::LEVELDB_STATUS_MAX + 1,
       base::Histogram::kUmaTargetedHistogramFlag);
+  base::trace_event::MemoryDumpManager::GetInstance()->RegisterDumpProvider(
+      this, base::ThreadTaskRunnerHandle::Get());
 }
 
 LeveldbValueStore::~LeveldbValueStore() {
   DCHECK_CURRENTLY_ON(BrowserThread::FILE);
+  base::trace_event::MemoryDumpManager::GetInstance()->UnregisterDumpProvider(
+      this);
 
   // Delete the database from disk if it's empty (but only if we managed to
   // open it!). This is safe on destruction, assuming that we have exclusive
@@ -325,6 +333,31 @@ bool LeveldbValueStore::WriteToDbForTest(leveldb::WriteBatch* batch) {
   return !WriteToDb(batch).get();
 }
 
+bool LeveldbValueStore::OnMemoryDump(
+    const base::trace_event::MemoryDumpArgs& args,
+    base::trace_event::ProcessMemoryDump* pmd) {
+  DCHECK_CURRENTLY_ON(BrowserThread::FILE);
+  if (!db_)
+    return true;

[cmumford, 2015/10/15 18:35:44]

Should you be returning false here?

[ssid, 2015/11/04 11:41:49]

This has to return true for temporary failures and return false only for
permanent failures. If it returns false the provider is disabled forever.
So,returning true. I guess this value must be changed to an enum.

+
+  std::string value;
+  uint64 size;
+  bool res = db_->GetProperty("leveldb.approximate-memory-usage", &value);
+  DCHECK(res);

[cmumford, 2015/10/15 18:35:44]

What about returning false if GetProperty returns false? I'm OK with the DCHECK
- because we really know that leveldb will always succeed (assuming it's the
right version), but it'd be more future-proof to leveldb changes if we add this
check.

[ssid, 2015/11/04 11:41:49]

The DCHECK is placed so that if in future the api changes the build breaks and
we will fix it. Instead of silently ignoring the error.

+  base::StringToUint64(value, &size);

[cmumford, 2015/10/15 18:35:44]

I guess not super important to check this, but might not be a bad idea.

[ssid, 2015/11/04 11:41:49]

Done.

+
+  base::trace_event::MemoryAllocatorDump* dump = pmd->CreateAllocatorDump(

[cmumford, 2015/10/15 18:35:44]

You could make this "auto" if you want - but perfectly fine as-is.

[ssid, 2015/11/04 11:41:49]

Done.

+      "leveldb/value_store/" + open_histogram_->histogram_name());
+  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;
+}
+
 scoped_ptr<ValueStore::Error> LeveldbValueStore::EnsureDbIsOpen() {
   DCHECK_CURRENTLY_ON(BrowserThread::FILE);