add plugin camera desktop

plugins/camera_desktop/windows/photo_handler.h

@@ -0,0 +1,15 @@
+#pragma once
+
+#include <cstdint>
+#include <string>
+
+class PhotoHandler {
+ public:
+  // Writes |bgra| pixels (already flipped by the caller) as a JPEG to |path|.
+  // Returns true on success; sets |error| on failure.
+  static bool Write(const uint8_t* bgra, int width, int height,
+                    const std::wstring& path, std::string* error);
+
+  // Generates a unique temp-file path for a photo from |camera_id|.
+  static std::wstring GeneratePath(int camera_id);
+};