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/cpp/shuffleboard/SendableCameraWrapper.cpp

@@ -0,0 +1,46 @@
+/*----------------------------------------------------------------------------*/
+/* 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.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#include "frc/shuffleboard/SendableCameraWrapper.h"
+
+#include <cscore_oo.h>
+#include <wpi/DenseMap.h>
+
+#include "frc/smartdashboard/SendableBuilder.h"
+
+using namespace frc;
+
+namespace {
+constexpr const char* kProtocol = "camera_server://";
+wpi::DenseMap<int, std::unique_ptr<SendableCameraWrapper>> wrappers;
+}  // namespace
+
+SendableCameraWrapper& SendableCameraWrapper::Wrap(
+    const cs::VideoSource& source) {
+  return Wrap(source.GetHandle());
+}
+
+SendableCameraWrapper& SendableCameraWrapper::Wrap(CS_Source source) {
+  auto& wrapper = wrappers[static_cast<int>(source)];
+  if (!wrapper)
+    wrapper = std::make_unique<SendableCameraWrapper>(source, private_init{});
+  return *wrapper;
+}
+
+SendableCameraWrapper::SendableCameraWrapper(CS_Source source,
+                                             const private_init&)
+    : SendableBase(false), m_uri(kProtocol) {
+  CS_Status status = 0;
+  auto name = cs::GetSourceName(source, &status);
+  SetName(name);
+  m_uri += name;
+}
+
+void SendableCameraWrapper::InitSendable(SendableBuilder& builder) {
+  builder.AddStringProperty(".ShuffleboardURI", [this] { return m_uri; },
+                            nullptr);
+}