Mark monotonic_now and realtime_now as const

Change-Id: I054ecc9c3c64b77e3c2bfa452d996b03797fdf64
Signed-off-by: Austin Schuh <austin.schuh@bluerivertech.com>
diff --git a/aos/actions/actor.h b/aos/actions/actor.h
index 33e70f2..b906059 100644
--- a/aos/actions/actor.h
+++ b/aos/actions/actor.h
@@ -90,7 +90,7 @@
 
   ::aos::EventLoop *event_loop() { return event_loop_; }
 
-  ::aos::monotonic_clock::time_point monotonic_now() {
+  ::aos::monotonic_clock::time_point monotonic_now() const {
     return event_loop_->monotonic_now();
   }
 
diff --git a/aos/events/event_loop.h b/aos/events/event_loop.h
index c81fa1e..11368ae 100644
--- a/aos/events/event_loop.h
+++ b/aos/events/event_loop.h
@@ -542,8 +542,8 @@
   virtual ~EventLoop();
 
   // Current time.
-  virtual monotonic_clock::time_point monotonic_now() = 0;
-  virtual realtime_clock::time_point realtime_now() = 0;
+  virtual monotonic_clock::time_point monotonic_now() const = 0;
+  virtual realtime_clock::time_point realtime_now() const = 0;
 
   template <typename T>
   const Channel *GetChannel(const std::string_view channel_name) {
diff --git a/aos/events/logging/log_reader.h b/aos/events/logging/log_reader.h
index 5cccdeb..3eebba7 100644
--- a/aos/events/logging/log_reader.h
+++ b/aos/events/logging/log_reader.h
@@ -400,7 +400,7 @@
           ->node_event_loop_factory_->node();
     }
 
-    monotonic_clock::time_point monotonic_now() {
+    monotonic_clock::time_point monotonic_now() const {
       return node_event_loop_factory_->monotonic_now();
     }
 
diff --git a/aos/events/shm_event_loop.h b/aos/events/shm_event_loop.h
index 71dff4e..e51f21b 100644
--- a/aos/events/shm_event_loop.h
+++ b/aos/events/shm_event_loop.h
@@ -48,10 +48,10 @@
   // Exits the event loop.  Async safe.
   void Exit();
 
-  aos::monotonic_clock::time_point monotonic_now() override {
+  aos::monotonic_clock::time_point monotonic_now() const override {
     return aos::monotonic_clock::now();
   }
-  aos::realtime_clock::time_point realtime_now() override {
+  aos::realtime_clock::time_point realtime_now() const override {
     return aos::realtime_clock::now();
   }
 
diff --git a/aos/events/simulated_event_loop.cc b/aos/events/simulated_event_loop.cc
index 2a276e7..a2428a4 100644
--- a/aos/events/simulated_event_loop.cc
+++ b/aos/events/simulated_event_loop.cc
@@ -584,11 +584,11 @@
     send_delay_ = send_delay;
   }
 
-  monotonic_clock::time_point monotonic_now() override {
+  monotonic_clock::time_point monotonic_now() const override {
     return node_event_loop_factory_->monotonic_now();
   }
 
-  realtime_clock::time_point realtime_now() override {
+  realtime_clock::time_point realtime_now() const override {
     return node_event_loop_factory_->realtime_now();
   }