Change base::TickClock to a ref counted class.

ui/display/chromeos/x11/native_display_event_dispatcher_x11.cc

Index: ui/display/chromeos/x11/native_display_event_dispatcher_x11.cc
diff --git a/ui/display/chromeos/x11/native_display_event_dispatcher_x11.cc b/ui/display/chromeos/x11/native_display_event_dispatcher_x11.cc
index f5c2e2e929839f74e27b14e0dfde534c39fddf3b..4122d9987b4e7ce792d3c159e9a701e1c275c8cf 100644
--- a/ui/display/chromeos/x11/native_display_event_dispatcher_x11.cc
+++ b/ui/display/chromeos/x11/native_display_event_dispatcher_x11.cc
@@ -99,8 +99,8 @@ uint32_t NativeDisplayEventDispatcherX11::DispatchEvent(
 }
 
 void NativeDisplayEventDispatcherX11::SetTickClockForTest(
-    scoped_ptr<base::TickClock> tick_clock) {
-  tick_clock_ = tick_clock.Pass();
+    scoped_refptr<base::TickClock> tick_clock) {
+  tick_clock_.swap(tick_clock);

[Daniel Erat, 2014/10/21 16:30:10]

why swap() instead of just assigning it?

[rkc, 2014/10/21 16:54:42]

I was trying to follow this pattern that is being used a lot of places where
tick clocks were being passed in. Looking at the code, there doesn't seem to be
any performance benefit, and ideally refptr should be passed in as const-ref -
which would not allow .swap anyway.

Changed it here, and, well 30 other places :)

   startup_time_ = tick_clock_->NowTicks();
 }