Use FileDescriptorWatcher in DeviceMonitorLinux

device/hid/input_service_linux_unittest.cc

Index: device/hid/input_service_linux_unittest.cc
diff --git a/device/hid/input_service_linux_unittest.cc b/device/hid/input_service_linux_unittest.cc
index 8b93cb525618866ba058d4911311caa258afed30..4b65c7f8386f66dfce0962b954895373a80bb9e9 100644
--- a/device/hid/input_service_linux_unittest.cc
+++ b/device/hid/input_service_linux_unittest.cc
@@ -6,7 +6,9 @@
 
 #include <vector>
 
+#include "base/files/file_descriptor_watcher_posix.h"
 #include "base/message_loop/message_loop.h"
+#include "base/run_loop.h"
 #include "device/hid/input_service_linux.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ -14,8 +16,13 @@ namespace device {
 
 TEST(InputServiceLinux, Simple) {
   base::MessageLoopForIO message_loop;
+  base::FileDescriptorWatcher file_descriptor_watcher(&message_loop);
+
   InputServiceLinux* service = InputServiceLinux::GetInstance();
 
+  // Allow the FileDescriptorWatcher in DeviceMonitorLinux to start watching.
+  base::RunLoop().RunUntilIdle();
+
   ASSERT_TRUE(service);
   std::vector<InputServiceLinux::InputDeviceInfo> devices;
   service->GetDevices(&devices);