webrtc 原始碼中如何新新增一個類

webrtc 原始碼使用gn做構建指令碼，使用.ninja作為編譯指令碼，gn就類似於cmakelist.txt,而.ninja就類似於makefile，webrtc中的BUILD.gn就是構建指令碼gn檔案，構建的時候會通過BUILD.gn檔案生成工程檔案（例如vs工程檔案）和.ninja檔案。
下面舉個例子：
本人在實現windows版的檔案插播和桌面共享是需要修改webrtc原始碼，下面是修改gn檔案，路徑是webrtc/src/media/BUILD.gn, 內容如下：

sources = [
    "engine/adm_helpers.cc"
 
,
    "engine/adm_helpers.h",
    "engine/apm_helpers.cc",
    "engine/apm_helpers.h",
    "engine/nullwebrtcvideoengine.h",
    "engine/payload_type_mapper.cc",
    "engine/payload_type_mapper.h",
    "engine/simulcast.cc",
    "engine/simulcast.h",
    "engine/webrtcmediaengine.cc",
    "engine/webrtcmediaengine.h"
 
,
    "engine/webrtcvideocapturer.cc",
    "engine/webrtcvideocapturer.h",
    "../custom_video_capturer/capture_module_interface.h", 
    "../custom_video_capturer/custom_video_capture.h", 
    "../custom_video_capturer/custom_video_capture.cc",
    "../custom_video_capturer/video_capture.h",
    "../custom_video_capturer/video_capture.cc"
 
, 
    "engine/webrtcvideocapturerfactory.cc",
    "engine/webrtcvideocapturerfactory.h",
    "engine/webrtcvideodecoderfactory.cc",
    "engine/webrtcvideodecoderfactory.h",
    "engine/webrtcvideoencoderfactory.cc",
    "engine/webrtcvideoencoderfactory.h",
    "engine/webrtcvideoengine.cc",
    "engine/webrtcvideoengine.h",
    "engine/webrtcvoiceengine.cc",
    "engine/webrtcvoiceengine.h",
  ]

將自己的類加上之後，重新 gn gen out/Default –args=“target_os=\”win\” target_cpu=\”x86\” is_debug=false” –ide=vs2017 構建完成後，編譯就可以了。