Add the future storage framework for the BudgetDatabase.

chrome/browser/budget_service/budget_database.cc

+// 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 "chrome/browser/budget_service/budget_database.h"
+
+#include "chrome/browser/budget_service/budget.pb.h"
+#include "components/leveldb_proto/proto_database.h"

[Peter Beverloo, 2016/06/29 13:37:27]

nit: you already include this in the header file, no need to include it twice

[harkness, 2016/06/30 10:41:57]

Acknowledged.

+#include "components/leveldb_proto/proto_database_impl.h"
+#include "content/public/browser/browser_thread.h"
+
+namespace {
+// UMA are logged for the database with this string as part of the name.
+// They will be LevelDB.*.BackgroundBudgetService. Changes here should be
+// synchronized with histograms.xml.
+const char kDatabaseUMAName[] = "BackgroundBudgetService";

[Peter Beverloo, 2016/06/29 13:37:27]

nit: blank lines after lines 12 and 16.

[harkness, 2016/06/30 10:41:57]

Done.

+}  // namespace
+
+BudgetDatabase::BudgetDatabase(
+    const base::FilePath& database_dir,
+    const scoped_refptr<base::SequencedTaskRunner>& task_runner)
+    : db_(new leveldb_proto::ProtoDatabaseImpl<Budget>(task_runner)),
+      weak_ptr_factory_(this) {
+  db_->Init(kDatabaseUMAName, database_dir,
+            base::Bind(&BudgetDatabase::OnDatabaseInit,
+                       weak_ptr_factory_.GetWeakPtr()));
+}
+
+BudgetDatabase::~BudgetDatabase() {}
+
+void BudgetDatabase::OnDatabaseInit(bool success) {
+  // TODO(harkness): Consider caching the budget database now?

[Peter Beverloo, 2016/06/29 13:37:27]

Caching is an interesting question. A developer could hypothetically flood disk
I/O now by just getting their budget value over and over again. Do you have
thoughts about this?

[harkness, 2016/06/30 10:41:57]

I need to dig into the implementation of ProtoDatabase a bit more. When we were
talking earlier in the week, you mentioned that the implementation read
everything into memory on the first read, but I haven't found that happening in
the code.

If the underlying implementation doesn't have a cache, I want to add one in
BudgetDatabase, which is the reason I've got the TODO in there.

+}
+
+void BudgetDatabase::GetValue(const GURL& origin,
+                              const GetValueCallback& callback) {
+  db_->GetEntry(origin.spec(), callback);

[Peter Beverloo, 2016/06/29 13:37:27]

DCHECK_EQ(origin.GetOrigin(), origin);

(Also on line 43. Best to be pedantic when it comes down to persistent on-disk
storage.)

[harkness, 2016/06/30 10:41:57]

Done.

+}
+
+void BudgetDatabase::SetValue(const GURL& origin,
+                              const Budget& budget,
+                              const SetValueCallback& callback) {
+  std::unique_ptr<leveldb_proto::ProtoDatabase<Budget>::KeyEntryVector> entries(
+      new leveldb_proto::ProtoDatabase<Budget>::KeyEntryVector());
+  entries->push_back(std::make_pair(origin.spec(), budget));
+  std::unique_ptr<std::vector<std::string>> keys_to_remove(
+      new std::vector<std::string>());
+  db_->UpdateEntries(std::move(entries), std::move(keys_to_remove), callback);
+}