Add UMA for service worker navigation preload.

content/browser/service_worker/service_worker_fetch_dispatcher.cc

 // Copyright 2014 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 "content/browser/service_worker/service_worker_fetch_dispatcher.h"
 
 #include <string>
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 362 matching lines @@
   did_complete_ = true;
   net_log_.EndEvent(
       net::NetLogEventType::SERVICE_WORKER_DISPATCH_FETCH_EVENT,
       base::Bind(&NetLogFetchEventCallback, status, fetch_result));
 
   FetchCallback fetch_callback = fetch_callback_;
   scoped_refptr<ServiceWorkerVersion> version = version_;
   fetch_callback.Run(status, fetch_result, response, version);
 }
 
-void ServiceWorkerFetchDispatcher::MaybeStartNavigationPreload(
+bool ServiceWorkerFetchDispatcher::MaybeStartNavigationPreload(
     net::URLRequest* original_request) {
   if (resource_type_ != RESOURCE_TYPE_MAIN_FRAME &&
       resource_type_ != RESOURCE_TYPE_SUB_FRAME) {
-    return;
+    return false;
   }
   if (!version_->navigation_preload_state().enabled)
-    return;
+    return false;
   // TODO(horo): Currently NavigationPreload doesn't support request body.
   if (!request_->blob_uuid.empty())
-    return;
+    return false;
 
   ServiceWorkerVersion::NavigationPreloadSupportStatus support_status =
       version_->GetNavigationPreloadSupportStatus();
   if (support_status !=
       ServiceWorkerVersion::NavigationPreloadSupportStatus::SUPPORTED) {
-    return;
+    return false;
   }
 
   ResourceRequestInfoImpl* original_info =
       ResourceRequestInfoImpl::ForRequest(original_request);
   ResourceRequesterInfo* requester_info = original_info->requester_info();
   if (IsBrowserSideNavigationEnabled()) {
     DCHECK(requester_info->IsBrowserSideNavigation());
   } else {
     DCHECK(requester_info->IsRenderer());
     if (!requester_info->filter())
-      return;
+      return false;
   }
 
   DCHECK(!url_loader_factory_);
   mojom::URLLoaderFactoryPtr factory;
   URLLoaderFactoryImpl::Create(
       ResourceRequesterInfo::CreateForNavigationPreload(requester_info),
       mojo::MakeRequest(&url_loader_factory_));
 
   preload_handle_ = mojom::FetchEventPreloadHandle::New();
 
@@ skipping 43 matching lines @@
       mojo::MakeRequest(&url_loader_associated_ptr,
                         url_loader_factory_.associated_group()),
       original_info->GetRouteID(), request_id, request,
       std::move(url_loader_client_associated_ptr_info));
 
   std::unique_ptr<DelegatingURLLoader> url_loader(
       new DelegatingURLLoader(std::move(url_loader_associated_ptr)));
   preload_handle_->url_loader = url_loader->CreateInterfacePtrAndBind();
   url_loader_ = std::move(url_loader);
   url_loader_client_ = std::move(url_loader_client);
+  return true;
 }
 
 ServiceWorkerMetrics::EventType ServiceWorkerFetchDispatcher::GetEventType()
     const {
   if (request_->fetch_type == ServiceWorkerFetchType::FOREIGN_FETCH)
     return ServiceWorkerMetrics::EventType::FOREIGN_FETCH;
   return ResourceTypeToEventType(resource_type_);
 }
 
 }  // namespace content