make navigation speed settable

#452

demos/viewer/src/vrcontroller_navigation_behavior.cpp

@@ -81,6 +81,14 @@ void VRControllerNavigationBehavior::OnButtonSignal(
   }
 }
 
+float VRControllerNavigationBehavior::GetNavigationSpeed() const {
+  return speed_;
+}
+
+void VRControllerNavigationBehavior::SetNavigationSpeed(float speed) {
+  speed_ = speed;
+}
+
 phx::VRController* VRControllerNavigationBehavior::GetController() {
   for (auto controller : device_system_->GetDevices<phx::VRController>()) {
     if (controller->GetSide() == side_) {

demos/viewer/src/vrcontroller_navigation_behavior.hpp

@@ -46,6 +46,9 @@ class VRControllerNavigationBehavior : public phx::Behavior {
   void OnButtonSignal(phx::VRController::ButtonId id,
                       phx::VRController::ButtonEvent event);
 
+  float GetNavigationSpeed() const;
+  void SetNavigationSpeed(float speed);
+
  private:
   phx::DeviceSystem* device_system_;
   phx::VRController* GetController();