Use factory method to create screen capturer

src/screen_capturer/windows/wgc_session.h

@@ -0,0 +1,40 @@
+#ifndef _WGC_SESSION_H_
+#define _WGC_SESSION_H_
+
+#include <Windows.h>
+
+class WgcSession {
+ public:
+  struct wgc_session_frame {
+    unsigned int width;
+    unsigned int height;
+    unsigned int row_pitch;
+
+    const unsigned char *data;
+  };
+
+  class wgc_session_observer {
+   public:
+    virtual ~wgc_session_observer() {}
+    virtual void OnFrame(const wgc_session_frame &frame) = 0;
+  };
+
+ public:
+  virtual void Release() = 0;
+
+  virtual int Initialize(HWND hwnd) = 0;
+  virtual int Initialize(HMONITOR hmonitor) = 0;
+
+  virtual void RegisterObserver(wgc_session_observer *observer) = 0;
+
+  virtual int Start() = 0;
+  virtual int Stop() = 0;
+
+  virtual int Pause() = 0;
+  virtual int Resume() = 0;
+
+ protected:
+  virtual ~WgcSession(){};
+};
+
+#endif