ozone: evdev: Use task_is_slow := false for input device open

This doesn't do anything on linux. On windows it means the task may
perform a "long wait", which also doesn't apply here. Opening a device
is fast.

BUG=none
TEST=boot link_freon & type on the keyboard. input still works :)

Review URL: https://codereview.chromium.org/972803002

Cr-Commit-Position: refs/heads/master@{#318800}

ui/events/ozone/evdev/input_device_factory_evdev.cc

@@ -229,7 +229,7 @@ void InputDeviceFactoryEvdev::AddInputDevice(int id,
   base::WorkerPool::PostTask(FROM_HERE,
                              base::Bind(&OpenInputDevice, base::Passed(&params),
                                         task_runner_, reply_callback),
-                             true /* task_is_slow */);
+                             false /* task_is_slow */);
 }
 
 void InputDeviceFactoryEvdev::RemoveInputDevice(const base::FilePath& path) {