ServiceWorker request intercept plan 2: Add set_job_factory to URLRequestJob

net/url_request/url_request_job_manager.cc

Index: net/url_request/url_request_job_manager.cc
diff --git a/net/url_request/url_request_job_manager.cc b/net/url_request/url_request_job_manager.cc
index 9ccf1d4e352606eb483df898d7f7a32b83e7560d..de95c8fb14b7e3a0f96531cfb0e504b30fe6161d 100644
--- a/net/url_request/url_request_job_manager.cc
+++ b/net/url_request/url_request_job_manager.cc
@@ -55,9 +55,15 @@ URLRequestJob* URLRequestJobManager::CreateJob(
 
   // We do this here to avoid asking interceptors about unsupported schemes.
   const URLRequestJobFactory* job_factory = NULL;
-  job_factory = request->context()->job_factory();
-
   const std::string& scheme = request->url().scheme();  // already lowercase
+
+  // Use request-specific job factory if it is given.
+  job_factory = request->job_factory();
+  if (!job_factory || !job_factory->IsHandledProtocol(scheme)) {
+    // Otherwise use the request context's factory.
+    job_factory = request->context()->job_factory();
+  }
+
   if (job_factory) {
     if (!job_factory->IsHandledProtocol(scheme)) {
       return new URLRequestErrorJob(