Fix recursion bug in blocking a fetch and add a test

headless/public/util/testing/generic_url_request_mocks.h

 // Copyright 2016 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.
 
 #ifndef HEADLESS_PUBLIC_UTIL_TESTING_GENERIC_URL_REQUEST_MOCKS_H_
 #define HEADLESS_PUBLIC_UTIL_TESTING_GENERIC_URL_REQUEST_MOCKS_H_
 
 #include <memory>
 #include <string>
 
@@ skipping 26 matching lines @@
       GenericURLRequestJob::RewriteCallback callback) override;
 
   const GenericURLRequestJob::HttpResponse* MaybeMatchResource(
       const GURL& url,
       const net::HttpRequestHeaders& request_headers) override;
 
   void OnResourceLoadComplete(const GURL& final_url,
                               const std::string& mime_type,
                               int http_response_code) override;
 
+  void SetShouldBlock(bool should_block) { should_block_ = should_block; }
+
  private:
+  bool should_block_;
+
   DISALLOW_COPY_AND_ASSIGN(MockGenericURLRequestJobDelegate);
 };
 
 // TODO(alexclarke): We may be able to replace this with the CookieMonster.
 class MockCookieStore : public net::CookieStore {
  public:
   MockCookieStore();
   ~MockCookieStore() override;
 
   // net::CookieStore implementation:
@@ skipping 82 matching lines @@
 
  private:
   std::string response_data_;
 
   DISALLOW_COPY_AND_ASSIGN(MockURLRequestDelegate);
 };
 
 }  // namespace headless
 
 #endif  // HEADLESS_PUBLIC_UTIL_TESTING_GENERIC_URL_REQUEST_MOCKS_H_