Sets start on activities added after starting scenario test.

Bug: webrtc:9510
Change-Id: I814674d1c30369f3795847b0b299daafb1e47489
Reviewed-on: https://webrtc-review.googlesource.com/c/121427
Reviewed-by: Christoffer Rodbro <crodbro@webrtc.org>
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26542}
diff --git a/test/scenario/scenario.cc b/test/scenario/scenario.cc
index aade8c6..5291dc8 100644
--- a/test/scenario/scenario.cc
+++ b/test/scenario/scenario.cc
@@ -318,6 +318,9 @@
 RepeatedActivity* Scenario::Every(TimeDelta interval,
                                   std::function<void(TimeDelta)> function) {
   repeated_activities_.emplace_back(new RepeatedActivity(interval, function));
+  if (start_time_.IsFinite()) {
+    repeated_activities_.back()->SetStartTime(Now());
+  }
   return repeated_activities_.back().get();
 }
 
@@ -326,6 +329,9 @@
   auto function_with_argument = [function](TimeDelta) { function(); };
   repeated_activities_.emplace_back(
       new RepeatedActivity(interval, function_with_argument));
+  if (start_time_.IsFinite()) {
+    repeated_activities_.back()->SetStartTime(Now());
+  }
   return repeated_activities_.back().get();
 }