Remove the file thread from the service process.

The file thread is no longer used. TaskScheduler should be used for
all file operations.

Bug: 
Change-Id: Iba07dc70a721c2c84cdb7ac00b7d4be057ae83aa
Reviewed-on: https://chromium-review.googlesource.com/660599Reviewed-by: Gene Gutnik <gene@chromium.org>
Commit-Queue: Francois Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/master@{#501273}

chrome/service/service_process.cc

@@ -178,9 +178,7 @@ bool ServiceProcess::Initialize(base::MessageLoopForUI* message_loop,
   base::Thread::Options options;
   options.message_loop_type = base::MessageLoop::TYPE_IO;
   io_thread_.reset(new ServiceIOThread("ServiceProcess_IO"));
-  file_thread_.reset(new base::Thread("ServiceProcess_File"));
-  if (!io_thread_->StartWithOptions(options) ||
-      !file_thread_->StartWithOptions(options)) {
+  if (!io_thread_->StartWithOptions(options)) {
     NOTREACHED();
     Teardown();
     return false;
@@ -273,7 +271,6 @@ bool ServiceProcess::Teardown() {
   // background threads can cleanup.
   shutdown_event_.Signal();
   io_thread_.reset();
-  file_thread_.reset();
 
   if (base::TaskScheduler::GetInstance())
     base::TaskScheduler::GetInstance()->Shutdown();

chrome/service/service_process.h

@@ -64,14 +64,6 @@ class ServiceProcess : public ServiceIPCServer::Client,
     return io_thread_ ? io_thread_->task_runner() : nullptr;
   }
 
-  // Returns the SingleThreadTaskRunner for the service process file thread.
-  // Used to do I/O operations (not network requests or even file: URL requests)
-  // to avoid blocking the main thread. Returns null before Initialize is
-  // called and after Teardown is called.
-  scoped_refptr<base::SingleThreadTaskRunner> file_task_runner() {
-    return file_thread_ ? file_thread_->task_runner() : nullptr;
-  }
-
   // A global event object that is signalled when the main thread's message
   // loop exits. This gives background threads a way to observe the main
   // thread shutting down.
@@ -120,7 +112,6 @@ class ServiceProcess : public ServiceIPCServer::Client,
 
   std::unique_ptr<net::NetworkChangeNotifier> network_change_notifier_;
   std::unique_ptr<base::Thread> io_thread_;
-  std::unique_ptr<base::Thread> file_thread_;
   std::unique_ptr<cloud_print::CloudPrintProxy> cloud_print_proxy_;
   std::unique_ptr<ServiceProcessPrefs> service_prefs_;
   std::unique_ptr<ServiceIPCServer> ipc_server_;