Allow video sources to be added to Shuffleboard (#1453)

Add a Sendable wrapper for VideoSource objects.

Add convenience methods for adding video sources directly to containers
so users won't have to manually wrap video sources.

wpilibc/src/main/native/include/frc/shuffleboard/SendableCameraWrapper.h

@@ -0,0 +1,55 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2018 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.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#pragma once
+
+#include <string>
+
+#include <cscore_c.h>
+
+#include "frc/smartdashboard/SendableBase.h"
+
+namespace cs {
+class VideoSource;
+}  // namespace cs
+
+namespace frc {
+
+/**
+ * A wrapper to make video sources sendable and usable from Shuffleboard.
+ */
+class SendableCameraWrapper : public SendableBase {
+ private:
+  struct private_init {};
+
+ public:
+  /**
+   * Creates a new sendable wrapper. Private constructor to avoid direct
+   * instantiation with multiple wrappers floating around for the same camera.
+   *
+   * @param source the source to wrap
+   */
+  SendableCameraWrapper(CS_Source source, const private_init&);
+
+  /**
+   * Gets a sendable wrapper object for the given video source, creating the
+   * wrapper if one does not already exist for the source.
+   *
+   * @param source the video source to wrap
+   * @return a sendable wrapper object for the video source, usable in
+   * Shuffleboard via ShuffleboardTab::Add() and ShuffleboardLayout::Add()
+   */
+  static SendableCameraWrapper& Wrap(const cs::VideoSource& source);
+  static SendableCameraWrapper& Wrap(CS_Source source);
+
+  void InitSendable(SendableBuilder& builder) override;
+
+ private:
+  std::string m_uri;
+};
+
+}  // namespace frc