Make DownloadResourceThrottle robust to ContinueDownload being called before

chrome/browser/download/download_resource_throttle.cc

 // Copyright (c) 2012 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/download/download_resource_throttle.h"
 
 #include "base/bind.h"
 #include "chrome/browser/download/download_util.h"
 #include "content/public/browser/resource_throttle_controller.h"
 
 DownloadResourceThrottle::DownloadResourceThrottle(
     DownloadRequestLimiter* limiter,
     int render_process_id,
     int render_view_id,
     int request_id)
-    : request_allowed_(false),
+    : querying_limiter_(true),
+      request_allowed_(false),
       request_deferred_(false) {
   limiter->CanDownloadOnIOThread(
       render_process_id,
       render_view_id,
       request_id,
       base::Bind(&DownloadResourceThrottle::ContinueDownload,
                  AsWeakPtr()));
 }
 
 DownloadResourceThrottle::~DownloadResourceThrottle() {
 }
 
 void DownloadResourceThrottle::WillStartRequest(bool* defer) {
-  *defer = request_deferred_ = !request_allowed_;
+  WillDownload(defer);
 }
 
 void DownloadResourceThrottle::WillRedirectRequest(const GURL& new_url,
                                                    bool* defer) {
-  *defer = request_deferred_ = !request_allowed_;
+  WillDownload(defer);
 }
 
 void DownloadResourceThrottle::WillProcessResponse(bool* defer) {
-  *defer = request_deferred_ = !request_allowed_;
+  WillDownload(defer);
+}
+
+void DownloadResourceThrottle::WillDownload(bool* defer) {
+  DCHECK(!request_deferred_);
+
+  // Defer the download until we have the DownloadRequestLimiter result.
+  if (querying_limiter_) {
+    request_deferred_ = true;
+    *defer = true;
+    return;
+  }
+
+  if (!request_allowed_)
+    controller()->Cancel();
 }
 
 void DownloadResourceThrottle::ContinueDownload(bool allow) {
+  querying_limiter_ = false;
   request_allowed_ = allow;
+
   if (allow) {
-    // Presumes all downloads initiated by navigation using this throttle and
+    // Presumes all downloads initiated by navigation use this throttle and
     // nothing else does.
-    download_util::RecordDownloadSource(
-        download_util::INITIATED_BY_NAVIGATION);
+    download_util::RecordDownloadSource(download_util::INITIATED_BY_NAVIGATION);
   } else {
     download_util::RecordDownloadCount(download_util::BLOCKED_BY_THROTTLING);
   }
 
   if (request_deferred_) {
+    request_deferred_ = false;
     if (allow) {
       controller()->Resume();
     } else {
       controller()->Cancel();
     }
   }
 }