Introduce VerifiedRulesetDealer and its async Handle.

components/subresource_filter/content/browser/verified_ruleset_dealer.cc

Index: components/subresource_filter/content/browser/verified_ruleset_dealer.cc
diff --git a/components/subresource_filter/content/browser/verified_ruleset_dealer.cc b/components/subresource_filter/content/browser/verified_ruleset_dealer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..cb6b79d72d7bf828f5bbb0a94c87120b57822c3f
--- /dev/null
+++ b/components/subresource_filter/content/browser/verified_ruleset_dealer.cc
@@ -0,0 +1,81 @@
+// Copyright 2017 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 "components/subresource_filter/content/browser/verified_ruleset_dealer.h"
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/files/file.h"
+#include "base/location.h"
+#include "base/logging.h"
+#include "components/subresource_filter/core/common/indexed_ruleset.h"
+#include "components/subresource_filter/core/common/memory_mapped_ruleset.h"
+
+namespace subresource_filter {
+
+VerifiedRulesetDealer::VerifiedRulesetDealer() = default;
+VerifiedRulesetDealer::~VerifiedRulesetDealer() = default;
+
+void VerifiedRulesetDealer::SetRulesetFile(base::File ruleset_file) {
+  RulesetDealer::SetRulesetFile(std::move(ruleset_file));
+  status_ = RulesetVerificationStatus::NOT_VERIFIED;
+}
+
+scoped_refptr<const MemoryMappedRuleset> VerifiedRulesetDealer::GetRuleset() {
+  DCHECK(CalledOnValidThread());
+
+  // TODO(pkalinnikov): Record verification status to a histogram.
+  switch (status_) {
+    case RulesetVerificationStatus::NOT_VERIFIED: {
+      auto ruleset = RulesetDealer::GetRuleset();
+      if (ruleset &&
+          IndexedRulesetMatcher::Verify(ruleset->data(), ruleset->length())) {
+        status_ = RulesetVerificationStatus::INTACT;
+        return ruleset;
+      }
+      status_ = RulesetVerificationStatus::CORRUPT;
+      return nullptr;
+    }
+    case RulesetVerificationStatus::INTACT: {
+      auto ruleset = RulesetDealer::GetRuleset();
+      DCHECK(ruleset);
+      return ruleset;
+    }
+    case RulesetVerificationStatus::CORRUPT:
+      return nullptr;
+    default:
+      NOTREACHED();
+      return nullptr;
+  }
+}
+
+VerifiedRulesetDealer::Handle::Handle(
+    scoped_refptr<base::SequencedTaskRunner> task_runner)
+    : task_runner_(task_runner.get()),
+      dealer_(new VerifiedRulesetDealer,
+              base::OnTaskRunnerDeleter(std::move(task_runner))) {}
+
+VerifiedRulesetDealer::Handle::~Handle() = default;
+
+void VerifiedRulesetDealer::Handle::GetDealerAsync(
+    base::Callback<void(VerifiedRulesetDealer*)> callback) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+
+  // NOTE: Properties of the sequenced |task_runner| guarantee that the
+  // |callback| will always be provided with a valid pointer, because the
+  // corresponding task will be posted *before* a task to delete the pointer
+  // upon destruction of |this| Handler.
+  task_runner_->PostTask(FROM_HERE,
+                         base::Bind(std::move(callback), dealer_.get()));
+}
+
+void VerifiedRulesetDealer::Handle::SetRulesetFile(base::File file) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&VerifiedRulesetDealer::SetRulesetFile,
+                 base::Unretained(dealer_.get()), base::Passed(&file)));
+}
+
+}  // namespace subresource_filter