impl(bigtable): cancel refresh_timer_ in QueryPlan destructor (#15755)

Author: scotthart

google/cloud/bigtable/internal/query_plan.cc

@@ -35,6 +35,10 @@ std::shared_ptr<QueryPlan> QueryPlan::Create(
   return plan;
 }
 
+QueryPlan::~QueryPlan() {
+  if (refresh_timer_.valid()) refresh_timer_.cancel();
+}
+
 void QueryPlan::Initialize() {
   std::unique_lock<std::mutex> lock(mu_);
   if (state_ == RefreshState::kDone) ScheduleRefresh(lock);

google/cloud/bigtable/internal/query_plan.h

@@ -43,6 +43,8 @@ class QueryPlan : public std::enable_shared_from_this<QueryPlan> {
       StatusOr<google::bigtable::v2::PrepareQueryResponse> response,
       RefreshFn fn, std::shared_ptr<Clock> clock = std::make_shared<Clock>());
 
+  ~QueryPlan();
+
   // Invalidates the current QueryPlan and triggers a refresh.
   void Invalidate(Status status, std::string const& invalid_query_plan_id);