[subresource_filter] Move throttle insertion into the client

components/subresource_filter/content/browser/subresource_filter_safe_browsing_activation_throttle.cc

Index: components/subresource_filter/content/browser/subresource_filter_safe_browsing_activation_throttle.cc
diff --git a/components/subresource_filter/content/browser/subresource_filter_safe_browsing_activation_throttle.cc b/components/subresource_filter/content/browser/subresource_filter_safe_browsing_activation_throttle.cc
index 4d728239ced8a6a02b0dd5b64e52c2020a1896e8..9650b4a71a0e60f6cf8c99f4f350940fab175328 100644
--- a/components/subresource_filter/content/browser/subresource_filter_safe_browsing_activation_throttle.cc
+++ b/components/subresource_filter/content/browser/subresource_filter_safe_browsing_activation_throttle.cc
@@ -102,18 +102,27 @@ SubresourceFilterSafeBrowsingActivationThrottle::
     : 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,