base: Support setting thread priorities generically.

remoting/base/auto_thread.cc

Index: remoting/base/auto_thread.cc
diff --git a/remoting/base/auto_thread.cc b/remoting/base/auto_thread.cc
index d79af49faa6976fdd14eb4bbb903e6176af5cc6e..8a6244ee1fa2aa155698190730c04cfe65f4daa1 100644
--- a/remoting/base/auto_thread.cc
+++ b/remoting/base/auto_thread.cc
@@ -112,14 +112,14 @@ AutoThread::~AutoThread() {
   DCHECK(!startup_data_);
 
   // Wait for the thread to exit.
-  if (thread_) {
+  if (!thread_.is_null()) {
     base::PlatformThread::Join(thread_);
   }
 }
 
 scoped_refptr<AutoThreadTaskRunner> AutoThread::StartWithType(
     base::MessageLoop::Type type) {
-  DCHECK(!thread_);
+  DCHECK(thread_.is_null());
 #if defined(OS_WIN)
   DCHECK(com_init_type_ != COM_INIT_STA || type == base::MessageLoop::TYPE_UI);
 #endif