[subresource_filter] Move throttle insertion into the client

components/subresource_filter/content/browser/subresource_filter_safe_browsing_activation_throttle.cc

 // Copyright (c) 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/subresource_filter_safe_browsing_activation_throttle.h"
 
 #include <vector>
 
 #include "base/timer/timer.h"
 #include "components/safe_browsing_db/v4_local_database_manager.h"
@@ skipping 84 matching lines @@
 };
 
 SubresourceFilterSafeBrowsingActivationThrottle::
     SubresourceFilterSafeBrowsingActivationThrottle(
         content::NavigationHandle* handle,
         scoped_refptr<safe_browsing::SafeBrowsingDatabaseManager>
             database_manager)
     : NavigationThrottle(handle),
       io_task_runner_(content::BrowserThread::GetTaskRunnerForThread(
           content::BrowserThread::IO)),
-      database_client_(
-          new SubresourceFilterSafeBrowsingActivationThrottle::SBDatabaseClient(
-              std::move(database_manager),
-              AsWeakPtr(),
-              base::ThreadTaskRunnerHandle::Get()),
-          base::OnTaskRunnerDeleter(io_task_runner_)) {}
+      database_client_(nullptr, base::OnTaskRunnerDeleter(io_task_runner_)) {
+  // The throttle can be created without a valid database manager. If so, it
+  // becomes a pass-through throttle and should never defer.
+  if (database_manager) {
+    std::unique_ptr<SBDatabaseClient, base::OnTaskRunnerDeleter>
+        database_client(
+            new SubresourceFilterSafeBrowsingActivationThrottle::
+                SBDatabaseClient(std::move(database_manager), AsWeakPtr(),
+                                 base::ThreadTaskRunnerHandle::Get()),
+            base::OnTaskRunnerDeleter(io_task_runner_));
+    database_client_ = std::move(database_client);

[engedy, 2017/05/02 18:21:54]

nit: Does .reset() work for unique_ptr's with custom deleters?

[Charlie Harrison, 2017/05/02 20:08:49]

Nope, but you can use the move equality operator. I simplified this to use a
ternary op in the initializer list though.

+  }
+}
 
 SubresourceFilterSafeBrowsingActivationThrottle::
     ~SubresourceFilterSafeBrowsingActivationThrottle() {}
 
 content::NavigationThrottle::ThrottleCheckResult
 SubresourceFilterSafeBrowsingActivationThrottle::WillProcessResponse() {
+  if (!database_client_)
+    return content::NavigationThrottle::PROCEED;
   io_task_runner_->PostTask(
       FROM_HERE, base::Bind(&SubresourceFilterSafeBrowsingActivationThrottle::
                                 SBDatabaseClient::CheckUrlOnIO,
                             base::Unretained(database_client_.get()),
                             navigation_handle()->GetURL()));
   return content::NavigationThrottle::ThrottleCheckResult::DEFER;
 }
 
 const char*
 SubresourceFilterSafeBrowsingActivationThrottle::GetNameForLogging() {
@@ skipping 13 matching lines @@
 
     driver_factory->OnMainResourceMatchedSafeBrowsingBlacklist(
         url, std::vector<GURL>(), threat_type, pattern_type);
   }
   // TODO(https://crbug.com/704508): We should measure the delay introduces by
   // this check. Similarly, as it's done the Safe Browsing Resource throttle.
   navigation_handle()->Resume();
 }
 
 }  //  namespace subresource_filter