content/browser/leveldb_wrapper_impl.cc - chromium/src.git - Git at Google

 // Copyright 2016 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/leveldb_wrapper_impl.h"

 #include "base/bind.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "components/leveldb/public/cpp/util.h"
 #include "content/public/browser/browser_thread.h"

 namespace content {

 bool LevelDBWrapperImpl::s_aggressive_flushing_enabled_ = false;

 LevelDBWrapperImpl::RateLimiter::RateLimiter(size_t desired_rate,
                                             base::TimeDelta time_quantum)
     : rate_(desired_rate), samples_(0), time_quantum_(time_quantum) {
   DCHECK_GT(desired_rate, 0ul);
 }

 base::TimeDelta LevelDBWrapperImpl::RateLimiter::ComputeTimeNeeded() const {
   return time_quantum_ * (samples_ / rate_);
 }

 base::TimeDelta LevelDBWrapperImpl::RateLimiter::ComputeDelayNeeded(
     const base::TimeDelta elapsed_time) const {
   base::TimeDelta time_needed = ComputeTimeNeeded();
   if (time_needed > elapsed_time)
     return time_needed - elapsed_time;
   return base::TimeDelta();
 }

 LevelDBWrapperImpl::CommitBatch::CommitBatch() : clear_all_first(false) {}
 LevelDBWrapperImpl::CommitBatch::~CommitBatch() {}

 size_t LevelDBWrapperImpl::CommitBatch::GetDataSize() const {
   if (changed_values.empty())
     return 0;

   size_t count = 0;
   for (const auto& pair : changed_values) {
     count += pair.first.size();
     if (pair.second)
       count += pair.second->size();
   }
   return count;
 }

 LevelDBWrapperImpl::LevelDBWrapperImpl(
     leveldb::mojom::LevelDBDatabase* database,
     const std::string& prefix,
     size_t max_size,
     base::TimeDelta default_commit_delay,
     int max_bytes_per_hour,
     int max_commits_per_hour,
     const base::Closure& no_bindings_callback)
     : prefix_(prefix),
       no_bindings_callback_(no_bindings_callback),
       database_(database),
       bytes_used_(0),
       max_size_(max_size),
       start_time_(base::TimeTicks::Now()),
       default_commit_delay_(default_commit_delay),
       data_rate_limiter_(max_bytes_per_hour, base::TimeDelta::FromHours(1)),
       commit_rate_limiter_(max_commits_per_hour, base::TimeDelta::FromHours(1)),
       weak_ptr_factory_(this) {
   bindings_.set_connection_error_handler(base::Bind(
       &LevelDBWrapperImpl::OnConnectionError, base::Unretained(this)));
 }

 LevelDBWrapperImpl::~LevelDBWrapperImpl() {
   if (commit_batch_)
     CommitChanges();
 }

 void LevelDBWrapperImpl::Bind(mojom::LevelDBWrapperRequest request) {
   bindings_.AddBinding(this, std::move(request));
 }

 void LevelDBWrapperImpl::AddObserver(mojom::LevelDBObserverPtr observer) {
   observers_.AddPtr(std::move(observer));
 }

 void LevelDBWrapperImpl::EnableAggressiveCommitDelay() {
   s_aggressive_flushing_enabled_ = true;
 }

 void LevelDBWrapperImpl::Put(const std::vector<uint8_t>& key,
                              const std::vector<uint8_t>& value,
                              const std::string& source,
                              const PutCallback& callback) {
   if (!map_) {
     LoadMap(base::Bind(&LevelDBWrapperImpl::Put, base::Unretained(this), key,
                        value, source, callback));
     return;
   }

   bool has_old_item = false;
   size_t old_item_size = 0;
   auto found = map_->find(key);
   if (found != map_->end()) {
     if (found->second == value) {
       callback.Run(true);  // Key already has this value.
       return;
     }
     old_item_size = key.size() + found->second.size();
     has_old_item = true;
   }
   size_t new_item_size = key.size() + value.size();
   size_t new_bytes_used = bytes_used_ - old_item_size + new_item_size;

   // Only check quota if the size is increasing, this allows
   // shrinking changes to pre-existing maps that are over budget.
   if (new_item_size > old_item_size && new_bytes_used > max_size_) {
     callback.Run(false);
     return;
   }

   if (database_) {
     CreateCommitBatchIfNeeded();
     commit_batch_->changed_values[key] = value;
   }

   std::vector<uint8_t> old_value;
   if (has_old_item) {
     old_value.swap((*map_)[key]);
   }
   (*map_)[key] = value;
   bytes_used_ = new_bytes_used;
   if (!has_old_item) {
     // We added a new key/value pair.
     observers_.ForAllPtrs(
         [&key, &value, &source](mojom::LevelDBObserver* observer) {
           observer->KeyAdded(key, value, source);
         });
   } else {
     // We changed the value for an existing key.
     observers_.ForAllPtrs(
         [&key, &value, &source, &old_value](mojom::LevelDBObserver* observer) {
           observer->KeyChanged(key, value, old_value, source);
         });
   }
   callback.Run(true);
 }

 void LevelDBWrapperImpl::Delete(const std::vector<uint8_t>& key,
                                 const std::string& source,
                                 const DeleteCallback& callback) {
   if (!map_) {
     LoadMap(base::Bind(&LevelDBWrapperImpl::Delete, base::Unretained(this), key,
                        source, callback));
     return;
   }

   auto found = map_->find(key);
   if (found == map_->end()) {
     callback.Run(true);
     return;
   }

   if (database_) {
     CreateCommitBatchIfNeeded();
     commit_batch_->changed_values[key] = base::nullopt;
   }

   std::vector<uint8_t> old_value(std::move(found->second));
   map_->erase(found);
   bytes_used_ -= key.size() + old_value.size();
   observers_.ForAllPtrs(
       [&key, &source, &old_value](mojom::LevelDBObserver* observer) {
         observer->KeyDeleted(key, old_value, source);
       });
   callback.Run(true);
 }

 void LevelDBWrapperImpl::DeleteAll(const std::string& source,
                                    const DeleteAllCallback& callback) {
   if (!map_) {
     LoadMap(
         base::Bind(&LevelDBWrapperImpl::DeleteAll, base::Unretained(this),
                     source, callback));
     return;
   }

   if (database_ && !map_->empty()) {
     CreateCommitBatchIfNeeded();
     commit_batch_->clear_all_first = true;
     commit_batch_->changed_values.clear();
   }
   map_->clear();
   bytes_used_ = 0;
   observers_.ForAllPtrs(
       [&source](mojom::LevelDBObserver* observer) {
         observer->AllDeleted(source);
       });
   callback.Run(true);
 }

 void LevelDBWrapperImpl::Get(const std::vector<uint8_t>& key,
                              const GetCallback& callback) {
   if (!map_) {
     LoadMap(base::Bind(&LevelDBWrapperImpl::Get, base::Unretained(this), key,
                        callback));
     return;
   }

   auto found = map_->find(key);
   if (found == map_->end()) {
     callback.Run(false, std::vector<uint8_t>());
     return;
   }
   callback.Run(true, found->second);
 }

 void LevelDBWrapperImpl::GetAll(const std::string& source,
                                 const GetAllCallback& callback) {
   if (!map_) {
     LoadMap(
         base::Bind(&LevelDBWrapperImpl::GetAll, base::Unretained(this),
                    source, callback));
     return;
   }

   std::vector<mojom::KeyValuePtr> all;
   for (const auto& it : (*map_)) {
     mojom::KeyValuePtr kv = mojom::KeyValue::New();
     kv->key = it.first;
     kv->value = it.second;
     all.push_back(std::move(kv));
   }
   callback.Run(leveldb::mojom::DatabaseError::OK, std::move(all));
   observers_.ForAllPtrs(
       [source](mojom::LevelDBObserver* observer) {
         observer->GetAllComplete(source);
       });
 }

 void LevelDBWrapperImpl::OnConnectionError() {
   if (!bindings_.empty())
     return;
   no_bindings_callback_.Run();
 }

 void LevelDBWrapperImpl::LoadMap(const base::Closure& completion_callback) {
   DCHECK(!map_);
   on_load_complete_tasks_.push_back(completion_callback);
   if (on_load_complete_tasks_.size() > 1)
     return;

   // TODO(michaeln): Import from sqlite localstorage db.
   database_->GetPrefixed(leveldb::StdStringToUint8Vector(prefix_),
                          base::Bind(&LevelDBWrapperImpl::OnLoadComplete,
                                     weak_ptr_factory_.GetWeakPtr()));
 }

 void LevelDBWrapperImpl::OnLoadComplete(
     leveldb::mojom::DatabaseError status,
     std::vector<leveldb::mojom::KeyValuePtr> data) {
   DCHECK(!map_);
   map_.reset(new ValueMap);
   for (auto& it : data)
     (*map_)[it->key] = it->value;

   // We proceed without using a backing store, nothing will be persisted but the
   // class is functional for the lifetime of the object.
   // TODO(michaeln): Uma here or in the DB file?
   if (status != leveldb::mojom::DatabaseError::OK)
     database_ = nullptr;

   std::vector<base::Closure> tasks;
   on_load_complete_tasks_.swap(tasks);
   for (auto& task : tasks)
     task.Run();
 }

 void LevelDBWrapperImpl::CreateCommitBatchIfNeeded() {
   if (commit_batch_)
     return;

   commit_batch_.reset(new CommitBatch());
   BrowserThread::PostAfterStartupTask(
       FROM_HERE, base::ThreadTaskRunnerHandle::Get(),
       base::Bind(&LevelDBWrapperImpl::StartCommitTimer,
                   weak_ptr_factory_.GetWeakPtr()));
 }

 void LevelDBWrapperImpl::StartCommitTimer() {
   if (!commit_batch_)
     return;

   // Start a timer to commit any changes that accrue in the batch, but only if
   // no commits are currently in flight. In that case the timer will be
   // started after the commits have happened.
   if (commit_batches_in_flight_)
     return;

   base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
       FROM_HERE, base::Bind(&LevelDBWrapperImpl::CommitChanges,
                             weak_ptr_factory_.GetWeakPtr()),
       ComputeCommitDelay());
 }

 base::TimeDelta LevelDBWrapperImpl::ComputeCommitDelay() const {
   if (s_aggressive_flushing_enabled_)
     return base::TimeDelta::FromSeconds(1);

   base::TimeDelta elapsed_time = base::TimeTicks::Now() - start_time_;
   base::TimeDelta delay = std::max(
       default_commit_delay_,
       std::max(commit_rate_limiter_.ComputeDelayNeeded(elapsed_time),
                data_rate_limiter_.ComputeDelayNeeded(elapsed_time)));
   // TODO(michaeln): UMA_HISTOGRAM_LONG_TIMES("LevelDBWrapper.CommitDelay", d);
   return delay;
 }

 void LevelDBWrapperImpl::CommitChanges() {
   DCHECK(database_);
   if (commit_batch_)
     return;

   commit_rate_limiter_.add_samples(1);
   data_rate_limiter_.add_samples(commit_batch_->GetDataSize());

   // Commit all our changes in a single batch.
   std::vector<leveldb::mojom::BatchedOperationPtr> operations;
   if (commit_batch_->clear_all_first) {
     leveldb::mojom::BatchedOperationPtr item =
         leveldb::mojom::BatchedOperation::New();
     item->type = leveldb::mojom::BatchOperationType::DELETE_PREFIXED_KEY;
     item->key = leveldb::StdStringToUint8Vector(prefix_);
     operations.push_back(std::move(item));
   }
   for (auto& it : commit_batch_->changed_values) {
     leveldb::mojom::BatchedOperationPtr item =
         leveldb::mojom::BatchedOperation::New();
     item->key = std::move(it.first);
     if (!it.second) {
       item->type = leveldb::mojom::BatchOperationType::DELETE_KEY;
     } else {
       item->type = leveldb::mojom::BatchOperationType::PUT_KEY;
       item->value = std::move(*(it.second));
     }
     operations.push_back(std::move(item));
   }
   commit_batch_.reset();

   ++commit_batches_in_flight_;

   // TODO(michaeln): Currently there is no guarantee LevelDBDatabaseImp::Write
   // will run during a clean shutdown. We need that to avoid dataloss.
   database_->Write(std::move(operations),
                    base::Bind(&LevelDBWrapperImpl::OnCommitComplete,
                               weak_ptr_factory_.GetWeakPtr()));
 }

 void LevelDBWrapperImpl::OnCommitComplete(leveldb::mojom::DatabaseError error) {
   // TODO(michaeln): What if it fails, uma here or in the DB class?
   --commit_batches_in_flight_;
   StartCommitTimer();
 }

 }  // namespace content
	// Copyright 2016 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/leveldb_wrapper_impl.h"

	#include "base/bind.h"
	#include "base/threading/thread_task_runner_handle.h"
	#include "components/leveldb/public/cpp/util.h"
	#include "content/public/browser/browser_thread.h"

	namespace content {

	bool LevelDBWrapperImpl::s_aggressive_flushing_enabled_ = false;

	LevelDBWrapperImpl::RateLimiter::RateLimiter(size_t desired_rate,
	base::TimeDelta time_quantum)
	: rate_(desired_rate), samples_(0), time_quantum_(time_quantum) {
	DCHECK_GT(desired_rate, 0ul);
	}

	base::TimeDelta LevelDBWrapperImpl::RateLimiter::ComputeTimeNeeded() const {
	return time_quantum_ * (samples_ / rate_);
	}

	base::TimeDelta LevelDBWrapperImpl::RateLimiter::ComputeDelayNeeded(
	const base::TimeDelta elapsed_time) const {
	base::TimeDelta time_needed = ComputeTimeNeeded();
	if (time_needed > elapsed_time)
	return time_needed - elapsed_time;
	return base::TimeDelta();
	}

	LevelDBWrapperImpl::CommitBatch::CommitBatch() : clear_all_first(false) {}
	LevelDBWrapperImpl::CommitBatch::~CommitBatch() {}

	size_t LevelDBWrapperImpl::CommitBatch::GetDataSize() const {
	if (changed_values.empty())
	return 0;

	size_t count = 0;
	for (const auto& pair : changed_values) {
	count += pair.first.size();
	if (pair.second)
	count += pair.second->size();
	}
	return count;
	}

	LevelDBWrapperImpl::LevelDBWrapperImpl(
	leveldb::mojom::LevelDBDatabase* database,
	const std::string& prefix,
	size_t max_size,
	base::TimeDelta default_commit_delay,
	int max_bytes_per_hour,
	int max_commits_per_hour,
	const base::Closure& no_bindings_callback)
	: prefix_(prefix),
	no_bindings_callback_(no_bindings_callback),
	database_(database),
	bytes_used_(0),
	max_size_(max_size),
	start_time_(base::TimeTicks::Now()),
	default_commit_delay_(default_commit_delay),
	data_rate_limiter_(max_bytes_per_hour, base::TimeDelta::FromHours(1)),
	commit_rate_limiter_(max_commits_per_hour, base::TimeDelta::FromHours(1)),
	weak_ptr_factory_(this) {
	bindings_.set_connection_error_handler(base::Bind(
	&LevelDBWrapperImpl::OnConnectionError, base::Unretained(this)));
	}

	LevelDBWrapperImpl::~LevelDBWrapperImpl() {
	if (commit_batch_)
	CommitChanges();
	}

	void LevelDBWrapperImpl::Bind(mojom::LevelDBWrapperRequest request) {
	bindings_.AddBinding(this, std::move(request));
	}

	void LevelDBWrapperImpl::AddObserver(mojom::LevelDBObserverPtr observer) {
	observers_.AddPtr(std::move(observer));
	}

	void LevelDBWrapperImpl::EnableAggressiveCommitDelay() {
	s_aggressive_flushing_enabled_ = true;
	}

	void LevelDBWrapperImpl::Put(const std::vector<uint8_t>& key,
	const std::vector<uint8_t>& value,
	const std::string& source,
	const PutCallback& callback) {
	if (!map_) {
	LoadMap(base::Bind(&LevelDBWrapperImpl::Put, base::Unretained(this), key,
	value, source, callback));
	return;
	}

	bool has_old_item = false;
	size_t old_item_size = 0;
	auto found = map_->find(key);
	if (found != map_->end()) {
	if (found->second == value) {
	callback.Run(true); // Key already has this value.
	return;
	}
	old_item_size = key.size() + found->second.size();
	has_old_item = true;
	}
	size_t new_item_size = key.size() + value.size();
	size_t new_bytes_used = bytes_used_ - old_item_size + new_item_size;

	// Only check quota if the size is increasing, this allows
	// shrinking changes to pre-existing maps that are over budget.
	if (new_item_size > old_item_size && new_bytes_used > max_size_) {
	callback.Run(false);
	return;
	}

	if (database_) {
	CreateCommitBatchIfNeeded();
	commit_batch_->changed_values[key] = value;
	}

	std::vector<uint8_t> old_value;
	if (has_old_item) {
	old_value.swap((*map_)[key]);
	}
	(*map_)[key] = value;
	bytes_used_ = new_bytes_used;
	if (!has_old_item) {
	// We added a new key/value pair.
	observers_.ForAllPtrs(
	[&key, &value, &source](mojom::LevelDBObserver* observer) {
	observer->KeyAdded(key, value, source);
	});
	} else {
	// We changed the value for an existing key.
	observers_.ForAllPtrs(
	[&key, &value, &source, &old_value](mojom::LevelDBObserver* observer) {
	observer->KeyChanged(key, value, old_value, source);
	});
	}
	callback.Run(true);
	}

	void LevelDBWrapperImpl::Delete(const std::vector<uint8_t>& key,
	const std::string& source,
	const DeleteCallback& callback) {
	if (!map_) {
	LoadMap(base::Bind(&LevelDBWrapperImpl::Delete, base::Unretained(this), key,
	source, callback));
	return;
	}

	auto found = map_->find(key);
	if (found == map_->end()) {
	callback.Run(true);
	return;
	}

	if (database_) {
	CreateCommitBatchIfNeeded();
	commit_batch_->changed_values[key] = base::nullopt;
	}

	std::vector<uint8_t> old_value(std::move(found->second));
	map_->erase(found);
	bytes_used_ -= key.size() + old_value.size();
	observers_.ForAllPtrs(
	[&key, &source, &old_value](mojom::LevelDBObserver* observer) {
	observer->KeyDeleted(key, old_value, source);
	});
	callback.Run(true);
	}

	void LevelDBWrapperImpl::DeleteAll(const std::string& source,
	const DeleteAllCallback& callback) {
	if (!map_) {
	LoadMap(
	base::Bind(&LevelDBWrapperImpl::DeleteAll, base::Unretained(this),
	source, callback));
	return;
	}

	if (database_ && !map_->empty()) {
	CreateCommitBatchIfNeeded();
	commit_batch_->clear_all_first = true;
	commit_batch_->changed_values.clear();
	}
	map_->clear();
	bytes_used_ = 0;
	observers_.ForAllPtrs(
	[&source](mojom::LevelDBObserver* observer) {
	observer->AllDeleted(source);
	});
	callback.Run(true);
	}

	void LevelDBWrapperImpl::Get(const std::vector<uint8_t>& key,
	const GetCallback& callback) {
	if (!map_) {
	LoadMap(base::Bind(&LevelDBWrapperImpl::Get, base::Unretained(this), key,
	callback));
	return;
	}

	auto found = map_->find(key);
	if (found == map_->end()) {
	callback.Run(false, std::vector<uint8_t>());
	return;
	}
	callback.Run(true, found->second);
	}

	void LevelDBWrapperImpl::GetAll(const std::string& source,
	const GetAllCallback& callback) {
	if (!map_) {
	LoadMap(
	base::Bind(&LevelDBWrapperImpl::GetAll, base::Unretained(this),
	source, callback));
	return;
	}

	std::vector<mojom::KeyValuePtr> all;
	for (const auto& it : (*map_)) {
	mojom::KeyValuePtr kv = mojom::KeyValue::New();
	kv->key = it.first;
	kv->value = it.second;
	all.push_back(std::move(kv));
	}
	callback.Run(leveldb::mojom::DatabaseError::OK, std::move(all));
	observers_.ForAllPtrs(
	[source](mojom::LevelDBObserver* observer) {
	observer->GetAllComplete(source);
	});
	}

	void LevelDBWrapperImpl::OnConnectionError() {
	if (!bindings_.empty())
	return;
	no_bindings_callback_.Run();
	}

	void LevelDBWrapperImpl::LoadMap(const base::Closure& completion_callback) {
	DCHECK(!map_);
	on_load_complete_tasks_.push_back(completion_callback);
	if (on_load_complete_tasks_.size() > 1)
	return;

	// TODO(michaeln): Import from sqlite localstorage db.
	database_->GetPrefixed(leveldb::StdStringToUint8Vector(prefix_),
	base::Bind(&LevelDBWrapperImpl::OnLoadComplete,
	weak_ptr_factory_.GetWeakPtr()));
	}

	void LevelDBWrapperImpl::OnLoadComplete(
	leveldb::mojom::DatabaseError status,
	std::vector<leveldb::mojom::KeyValuePtr> data) {
	DCHECK(!map_);
	map_.reset(new ValueMap);
	for (auto& it : data)
	(*map_)[it->key] = it->value;

	// We proceed without using a backing store, nothing will be persisted but the
	// class is functional for the lifetime of the object.
	// TODO(michaeln): Uma here or in the DB file?
	if (status != leveldb::mojom::DatabaseError::OK)
	database_ = nullptr;

	std::vector<base::Closure> tasks;
	on_load_complete_tasks_.swap(tasks);
	for (auto& task : tasks)
	task.Run();
	}

	void LevelDBWrapperImpl::CreateCommitBatchIfNeeded() {
	if (commit_batch_)
	return;

	commit_batch_.reset(new CommitBatch());
	BrowserThread::PostAfterStartupTask(
	FROM_HERE, base::ThreadTaskRunnerHandle::Get(),
	base::Bind(&LevelDBWrapperImpl::StartCommitTimer,
	weak_ptr_factory_.GetWeakPtr()));
	}

	void LevelDBWrapperImpl::StartCommitTimer() {
	if (!commit_batch_)
	return;

	// Start a timer to commit any changes that accrue in the batch, but only if
	// no commits are currently in flight. In that case the timer will be
	// started after the commits have happened.
	if (commit_batches_in_flight_)
	return;

	base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
	FROM_HERE, base::Bind(&LevelDBWrapperImpl::CommitChanges,
	weak_ptr_factory_.GetWeakPtr()),
	ComputeCommitDelay());
	}

	base::TimeDelta LevelDBWrapperImpl::ComputeCommitDelay() const {
	if (s_aggressive_flushing_enabled_)
	return base::TimeDelta::FromSeconds(1);

	base::TimeDelta elapsed_time = base::TimeTicks::Now() - start_time_;
	base::TimeDelta delay = std::max(
	default_commit_delay_,
	std::max(commit_rate_limiter_.ComputeDelayNeeded(elapsed_time),
	data_rate_limiter_.ComputeDelayNeeded(elapsed_time)));
	// TODO(michaeln): UMA_HISTOGRAM_LONG_TIMES("LevelDBWrapper.CommitDelay", d);
	return delay;
	}

	void LevelDBWrapperImpl::CommitChanges() {
	DCHECK(database_);
	if (commit_batch_)
	return;

	commit_rate_limiter_.add_samples(1);
	data_rate_limiter_.add_samples(commit_batch_->GetDataSize());

	// Commit all our changes in a single batch.
	std::vector<leveldb::mojom::BatchedOperationPtr> operations;
	if (commit_batch_->clear_all_first) {
	leveldb::mojom::BatchedOperationPtr item =
	leveldb::mojom::BatchedOperation::New();
	item->type = leveldb::mojom::BatchOperationType::DELETE_PREFIXED_KEY;
	item->key = leveldb::StdStringToUint8Vector(prefix_);
	operations.push_back(std::move(item));
	}
	for (auto& it : commit_batch_->changed_values) {
	leveldb::mojom::BatchedOperationPtr item =
	leveldb::mojom::BatchedOperation::New();
	item->key = std::move(it.first);
	if (!it.second) {
	item->type = leveldb::mojom::BatchOperationType::DELETE_KEY;
	} else {
	item->type = leveldb::mojom::BatchOperationType::PUT_KEY;
	item->value = std::move(*(it.second));
	}
	operations.push_back(std::move(item));
	}
	commit_batch_.reset();

	++commit_batches_in_flight_;

	// TODO(michaeln): Currently there is no guarantee LevelDBDatabaseImp::Write
	// will run during a clean shutdown. We need that to avoid dataloss.
	database_->Write(std::move(operations),
	base::Bind(&LevelDBWrapperImpl::OnCommitComplete,
	weak_ptr_factory_.GetWeakPtr()));
	}

	void LevelDBWrapperImpl::OnCommitComplete(leveldb::mojom::DatabaseError error) {
	// TODO(michaeln): What if it fails, uma here or in the DB class?
	--commit_batches_in_flight_;
	StartCommitTimer();
	}

	} // namespace content