[subresource_filter] Move throttle insertion into the client

components/subresource_filter/content/browser/subresource_filter_safe_browsing_activation_throttle.cc

 // 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/subresource_filter_safe_browsing_activation_throttle.h"
 
 #include <utility>
 #include <vector>
 
 #include "base/metrics/histogram_macros.h"
 #include "base/timer/timer.h"
 #include "components/subresource_filter/content/browser/content_subresource_filter_driver_factory.h"
 #include "components/subresource_filter/content/browser/subresource_filter_safe_browsing_client.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/navigation_handle.h"
 #include "content/public/browser/web_contents.h"
 
 namespace subresource_filter {
 
 SubresourceFilterSafeBrowsingActivationThrottle::
     SubresourceFilterSafeBrowsingActivationThrottle(
         content::NavigationHandle* handle,
         scoped_refptr<base::SingleThreadTaskRunner> io_task_runner,
         scoped_refptr<safe_browsing::SafeBrowsingDatabaseManager>
             database_manager)
     : NavigationThrottle(handle),
-      database_manager_(std::move(database_manager)),
-      io_task_runner_(io_task_runner),
-      database_client_(new SubresourceFilterSafeBrowsingClient(
-                           database_manager_,
-                           AsWeakPtr(),
-                           io_task_runner,
-                           base::ThreadTaskRunnerHandle::Get()),
+      io_task_runner_(std::move(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.
+      database_client_(database_manager
+                           ? new SubresourceFilterSafeBrowsingClient(
+                                 std::move(database_manager),
+                                 AsWeakPtr(),
+                                 io_task_runner_,
+                                 base::ThreadTaskRunnerHandle::Get())
+                           : nullptr,
                        base::OnTaskRunnerDeleter(io_task_runner_)) {}
 
 SubresourceFilterSafeBrowsingActivationThrottle::
     ~SubresourceFilterSafeBrowsingActivationThrottle() {
   // TODO(csharrison): Log metrics based on check_results_.
 }
 
 content::NavigationThrottle::ThrottleCheckResult
 SubresourceFilterSafeBrowsingActivationThrottle::WillStartRequest() {
   CheckCurrentUrl();
   return content::NavigationThrottle::ThrottleCheckResult::PROCEED;
 }
 
 content::NavigationThrottle::ThrottleCheckResult
 SubresourceFilterSafeBrowsingActivationThrottle::WillRedirectRequest() {
   CheckCurrentUrl();
   return content::NavigationThrottle::ThrottleCheckResult::PROCEED;
 }
 
 content::NavigationThrottle::ThrottleCheckResult
 SubresourceFilterSafeBrowsingActivationThrottle::WillProcessResponse() {
+  if (!database_client_)
+    return content::NavigationThrottle::PROCEED;
+
   // No need to defer the navigation if the check already happened.
   if (check_results_.back().finished) {
     NotifyResult();
     return content::NavigationThrottle::ThrottleCheckResult::PROCEED;
   }
   defer_time_ = base::TimeTicks::Now();
   return content::NavigationThrottle::ThrottleCheckResult::DEFER;
 }
 
 const char*
@@ skipping 10 matching lines @@
   auto& stored_result = check_results_.at(request_id);
   DCHECK(!stored_result.finished);
   stored_result = result;
   if (!defer_time_.is_null() && request_id == check_results_.size() - 1) {
     NotifyResult();
     navigation_handle()->Resume();
   }
 }
 
 void SubresourceFilterSafeBrowsingActivationThrottle::CheckCurrentUrl() {
+  if (!database_client_)
+    return;
   check_results_.emplace_back();
   size_t id = check_results_.size() - 1;
   io_task_runner_->PostTask(
       FROM_HERE, base::Bind(&SubresourceFilterSafeBrowsingClient::CheckUrlOnIO,
                             base::Unretained(database_client_.get()),
                             navigation_handle()->GetURL(), id));
 }
 
 void SubresourceFilterSafeBrowsingActivationThrottle::NotifyResult() {
   content::WebContents* web_contents = navigation_handle()->GetWebContents();
@@ skipping 21 matching lines @@
   // speculatively checks URLs on WillStartRequest. This is only different from
   // the actual delay if there was at least one redirect.
   base::TimeDelta no_redirect_speculation_delay =
       check_results_.size() > 1 ? result.check_time : delay;
   UMA_HISTOGRAM_TIMES(
       "SubresourceFilter.PageLoad.SafeBrowsingDelay.NoRedirectSpeculation",
       no_redirect_speculation_delay);
 }
 
 }  //  namespace subresource_filter