Change base::TickClock to a ref counted class.

components/copresence/handlers/audio/audio_directive_list.cc

Index: components/copresence/handlers/audio/audio_directive_list.cc
diff --git a/components/copresence/handlers/audio/audio_directive_list.cc b/components/copresence/handlers/audio/audio_directive_list.cc
index 8b9b76ec21d1945b9955ea17bba27e41e8b892c1..7d64971ee16bf12c45c1292713ffa47c78295afa 100644
--- a/components/copresence/handlers/audio/audio_directive_list.cc
+++ b/components/copresence/handlers/audio/audio_directive_list.cc
@@ -75,6 +75,13 @@ scoped_ptr<AudioDirective> AudioDirectiveList::GetActiveDirective() {
   return make_scoped_ptr(new AudioDirective(active_directives_.front()));
 }
 
+void AudioDirectiveList::set_clock_for_testing(
+    const scoped_refptr<base::TickClock>& clock) {
+  clock_ = clock;
+}
+
+// Private methods.
+
 std::vector<AudioDirective>::iterator AudioDirectiveList::FindDirectiveByOpId(
     const std::string& op_id) {
   for (std::vector<AudioDirective>::iterator it = active_directives_.begin();