Avoid copying in ranged for loops

New toolchain complains about this, and it's not on purpose.

Change-Id: I5e86f9ba46bc5232831df93718196712eaba89c0
Signed-off-by: Brian Silverman <bsilver16834@gmail.com>
diff --git a/aos/events/simulated_event_loop_test.cc b/aos/events/simulated_event_loop_test.cc
index 277e783..a94b895 100644
--- a/aos/events/simulated_event_loop_test.cc
+++ b/aos/events/simulated_event_loop_test.cc
@@ -2134,7 +2134,7 @@
   // Build up the list of all the messages we expect when we come back.
   {
     std::set<const aos::Channel *> statistics_channels;
-    for (const std::pair<std::string_view, const Node *> pi :
+    for (const std::pair<std::string_view, const Node *> &pi :
          std::vector<std::pair<std::string_view, const Node *>>{
              {"/pi1/aos", pi1->node()},
              {"/pi2/aos", pi1->node()},
@@ -2171,7 +2171,7 @@
   // forwarded, mainly the timestamp message.
   {
     std::set<const aos::Channel *> statistics_channels;
-    for (const std::pair<std::string_view, const Node *> pi :
+    for (const std::pair<std::string_view, const Node *> &pi :
          std::vector<std::pair<std::string_view, const Node *>>{
              {"/pi1/aos", pi1->node()}, {"/pi3/aos", pi1->node()}}) {
       statistics_channels.insert(configuration::GetChannel(
@@ -2202,7 +2202,7 @@
 
   {
     std::set<const aos::Channel *> statistics_channels;
-    for (const std::pair<std::string_view, const Node *> pi :
+    for (const std::pair<std::string_view, const Node *> &pi :
          std::vector<std::pair<std::string_view, const Node *>>{
              {"/pi1/aos", pi1->node()}, {"/pi3/aos", pi1->node()}}) {
       statistics_channels.insert(configuration::GetChannel(
diff --git a/y2018/control_loops/superstructure/arm/trajectory.cc b/y2018/control_loops/superstructure/arm/trajectory.cc
index bd67ce3..c6e09dd 100644
--- a/y2018/control_loops/superstructure/arm/trajectory.cc
+++ b/y2018/control_loops/superstructure/arm/trajectory.cc
@@ -130,7 +130,7 @@
     // Loop through all the various vmin, plan_vmax combinations.
     for (const double c : {-plan_vmax, plan_vmax}) {
       // Also loop through saturating theta0 and theta1
-      for (const ::std::tuple<double, double, double> abgravity :
+      for (const ::std::tuple<double, double, double> &abgravity :
            {::std::tuple<double, double, double>{vk1(0), vk2(0),
                                                 gravity_volts(0)},
             ::std::tuple<double, double, double>{vk1(1), vk2(1),
@@ -201,7 +201,7 @@
 
   double goal_acceleration = -::std::numeric_limits<double>::infinity();
   for (double c : {-plan_vmax, plan_vmax}) {
-    for (const ::std::pair<double, double> ab :
+    for (const ::std::pair<double, double> &ab :
          {::std::pair<double, double>{k_constant(0, 0), k_scalar(0, 0)},
           ::std::pair<double, double>{k_constant(1, 0), k_scalar(1, 0)}}) {
       const double a = ab.first;
@@ -259,7 +259,7 @@
 
   double goal_acceleration = -::std::numeric_limits<double>::infinity();
   for (double c : {-plan_vmax, plan_vmax}) {
-    for (const ::std::pair<double, double> ab :
+    for (const ::std::pair<double, double> &ab :
          {::std::pair<double, double>{k_constant(0, 0), k_scalar(0, 0)},
           ::std::pair<double, double>{k_constant(1, 0), k_scalar(1, 0)}}) {
       const double a = ab.first;