[wpilibc] Add ScopedTracer class (#2724)

This makes it easier for C++ teams to log a certain piece of code using RAII.

wpilibc/src/main/native/cpp/ScopedTracer.cpp

@@ -0,0 +1,22 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2020 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#include "frc/ScopedTracer.h"
+
+#include <wpi/raw_ostream.h>
+
+using namespace frc;
+
+ScopedTracer::ScopedTracer(wpi::Twine name, wpi::raw_ostream& os)
+    : m_name(name.str()), m_os(os) {
+  m_tracer.ResetTimer();
+}
+
+ScopedTracer::~ScopedTracer() {
+  m_tracer.AddEpoch(m_name);
+  m_tracer.PrintEpochs(m_os);
+}