Convert base::Bind in UserInputMonitorLinuxCore

This CL converts the OnXEvent callback to use base::BindRepeating.
RepeatingCallback is correct for this callback since OnXEvent is called
every time there is something to read from |x_record_display_|.

BUG=1007799

Change-Id: I2eb4630512c7d27f7cc6d852f7e2903bdf12142c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2283415
Auto-Submit: Matt Reynolds <mattreynolds@chromium.org>
Reviewed-by: Chrome Cunningham <chcunningham@chromium.org>
Commit-Queue: Chrome Cunningham <chcunningham@chromium.org>
Cr-Commit-Position: refs/heads/master@{#786007}

media/base/user_input_monitor_linux.cc

@@ -187,7 +187,8 @@ void UserInputMonitorLinuxCore::StartMonitor() {
   // from |x_record_display_|.
   watch_controller_ = base::FileDescriptorWatcher::WatchReadable(
       ConnectionNumber(x_record_display_),
-      base::Bind(&UserInputMonitorLinuxCore::OnXEvent, base::Unretained(this)));
+      base::BindRepeating(&UserInputMonitorLinuxCore::OnXEvent,
+                          base::Unretained(this)));
 
   // Start observing message loop destruction if we start monitoring the first
   // event.