Replace NULL with nullptr in all C++ files.

webrtc/test/vcm_capturer.cc

Index: webrtc/test/vcm_capturer.cc
diff --git a/webrtc/test/vcm_capturer.cc b/webrtc/test/vcm_capturer.cc
index 535e9bf219db24f370bd547e4d617eb8df724c1d..76eb48349b2977be91cb56e37803ffd8daaf6930 100644
--- a/webrtc/test/vcm_capturer.cc
+++ b/webrtc/test/vcm_capturer.cc
@@ -16,7 +16,7 @@
 namespace webrtc {
 namespace test {
 
-VcmCapturer::VcmCapturer() : started_(false), sink_(nullptr), vcm_(NULL) {}
+VcmCapturer::VcmCapturer() : started_(false), sink_(nullptr), vcm_(nullptr) {}
 
 bool VcmCapturer::Init(size_t width, size_t height, size_t target_fps) {
   VideoCaptureModule::DeviceInfo* device_info =
@@ -59,7 +59,7 @@ VcmCapturer* VcmCapturer::Create(size_t width,
   if (!vcm_capturer->Init(width, height, target_fps)) {
     // TODO(pbos): Log a warning that this failed.
     delete vcm_capturer;
-    return NULL;
+    return nullptr;
   }
   return vcm_capturer;
 }