Change base::TickClock to a ref counted class.

ash/wm/maximize_mode/maximize_mode_controller.cc

Index: ash/wm/maximize_mode/maximize_mode_controller.cc
diff --git a/ash/wm/maximize_mode/maximize_mode_controller.cc b/ash/wm/maximize_mode/maximize_mode_controller.cc
index dc78d281d2cb69534b0c687557cf5db7367ef887..55fe0a79a822ac7a238284c333ea642c8094683b 100644
--- a/ash/wm/maximize_mode/maximize_mode_controller.cc
+++ b/ash/wm/maximize_mode/maximize_mode_controller.cc
@@ -491,9 +491,9 @@ bool MaximizeModeController::WasLidOpenedRecently() const {
 }
 
 void MaximizeModeController::SetTickClockForTest(
-    scoped_ptr<base::TickClock> tick_clock) {
-  DCHECK(tick_clock_);
-  tick_clock_ = tick_clock.Pass();
+    scoped_refptr<base::TickClock> tick_clock) {
+  DCHECK(tick_clock_.get() != NULL);
+  tick_clock_.swap(tick_clock);
 }
 
 }  // namespace ash