remove a mutable_vector type function

mutable_vector does not seal the inner data well.
mutable_vector function loss the semantics in the particular expression.

modules/planning/common/speed_limit.cc

@@ -23,8 +23,19 @@
 namespace apollo {
 namespace planning {
 
-std::vector<SpeedPoint>* SpeedLimit::mutable_speed_limits() {
-  return &_speed_point;
+void SpeedLimit::add_speed_limit(const SpeedPoint& speed_point) {
+  _speed_point.push_back(speed_point);
+}
+
+void SpeedLimit::add_speed_limit(const double s, const double t, const double v,
+                                 const double a, const double da) {
+  SpeedPoint speed_point;
+  speed_point.set_s(s);
+  speed_point.set_t(t);
+  speed_point.set_v(v);
+  speed_point.set_a(a);
+  speed_point.set_da(da);
+  _speed_point.push_back(speed_point);
 }
 
 const std::vector<SpeedPoint>& SpeedLimit::speed_limits() const {

modules/planning/common/speed_limit.h

@@ -31,7 +31,9 @@ namespace planning {
 class SpeedLimit {
  public:
   SpeedLimit() = default;
-  std::vector<SpeedPoint>* mutable_speed_limits();
+  void add_speed_limit(const SpeedPoint& speed_point);
+  void add_speed_limit(const double s, const double t, const double v,
+                       const double a, const double da);
   const std::vector<SpeedPoint>& speed_limits() const;
 
  private:

modules/planning/optimizer/st_graph/st_boundary_mapper.cc

@@ -102,9 +102,9 @@ Status StBoundaryMapper::get_speed_limits(
   for (const auto& point : path_data.path().path_points()) {
     speed_limits.push_back(_st_boundary_config.maximal_speed());
     for (auto& lane : lanes) {
-      if (lane->is_on_lane( { point.x(), point.y() })) {
-        speed_limits.back() = std::fmin(speed_limits.back(),
-                                        lane->lane().speed_limit());
+      if (lane->is_on_lane({point.x(), point.y()})) {
+        speed_limits.back() =
+            std::fmin(speed_limits.back(), lane->lane().speed_limit());
         if (lane->lane().turn() == apollo::hdmap::Lane::U_TURN) {
           speed_limits.back() = std::fmin(
               speed_limits.back(), _st_boundary_config.speed_limit_on_u_turn());
@@ -153,8 +153,6 @@ Status StBoundaryMapper::get_speed_limits(
       curr_speed_limit *= _st_boundary_config.speed_multiply_buffer();
       curr_speed_limit =
           std::fmax(curr_speed_limit, _st_boundary_config.lowest_speed());
-      auto* mutable_speed_limits_data =
-          speed_limit_data->mutable_speed_limits();
 
       SpeedPoint speed_point;
       speed_point.set_s(s);
@@ -162,7 +160,7 @@ Status StBoundaryMapper::get_speed_limits(
       speed_point.set_v(curr_speed_limit);
       speed_point.set_a(0.0);
       speed_point.set_da(0.0);
-      mutable_speed_limits_data->push_back(speed_point);
+      speed_limit_data->add_speed_limit(speed_point);
 
       s += unit_s;
       ++i;