IndexedDB: Added UMA stat to measure time to close backing store.

content/browser/indexed_db/leveldb/leveldb_database.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/indexed_db/leveldb/leveldb_database.h"
 
 #include <cerrno>
 
 #include "base/basictypes.h"
 #include "base/files/file.h"
@@ skipping 66 matching lines @@
 void LevelDBDatabase::ComparatorAdapter::FindShortSuccessor(
     std::string* key) const {}
 
 LevelDBSnapshot::LevelDBSnapshot(LevelDBDatabase* db)
     : db_(db->db_.get()), snapshot_(db_->GetSnapshot()) {}
 
 LevelDBSnapshot::~LevelDBSnapshot() { db_->ReleaseSnapshot(snapshot_); }
 
 LevelDBDatabase::LevelDBDatabase() {}
 
 LevelDBDatabase::~LevelDBDatabase() {

[dgrogan, 2015/06/18 22:15:58]

Mainly for my edification:

Looks like this gets called when the ref count on an instance of
IndexedDBBackingStore drops to 0, is that right? Is there still a timer that
keeps the database open for 2 seconds?

[cmumford, 2015/06/18 22:20:14]

Yes, timer is still in IndexedDBFactoryImpl::ReleaseBackingStore(). So when the
timer closes the backing store (and eventually the LevelDBDatabase) this
function will be executed.

   // db_'s destructor uses comparator_adapter_; order of deletion is important.
-  db_.reset();
+  CloseDatabase();
   comparator_adapter_.reset();
   env_.reset();
 }
 
+void LevelDBDatabase::CloseDatabase() {
+  if (db_) {
+    base::TimeTicks begin_time = base::TimeTicks::Now();
+    db_.reset();
+    UMA_HISTOGRAM_MEDIUM_TIMES("WebCore.IndexedDB.LevelDB.CloseTime",
+                               base::TimeTicks::Now() - begin_time);
+  }
+}
+
 static leveldb::Status OpenDB(
     leveldb::Comparator* comparator,
     leveldb::Env* env,
     const base::FilePath& path,
     leveldb::DB** db,
     scoped_ptr<const leveldb::FilterPolicy>* filter_policy) {
   filter_policy->reset(leveldb::NewBloomFilterPolicy(10));
   leveldb::Options options;
   options.comparator = comparator;
   options.create_if_missing = true;
@@ skipping 313 matching lines @@
   const leveldb::Slice start_slice = MakeSlice(start);
   const leveldb::Slice stop_slice = MakeSlice(stop);
   // NULL batch means just wait for earlier writes to be done
   db_->Write(leveldb::WriteOptions(), NULL);
   db_->CompactRange(&start_slice, &stop_slice);
 }
 
 void LevelDBDatabase::CompactAll() { db_->CompactRange(NULL, NULL); }
 
 }  // namespace content