Add Jpeg frame writer for test support.

webrtc/test/testsupport/frame_writer.h

Index: webrtc/test/testsupport/frame_writer.h
diff --git a/webrtc/test/testsupport/frame_writer.h b/webrtc/test/testsupport/frame_writer.h
index 76298498ac68bc27ae407316639c0e36c75fb52d..d4077982037bca7fc515fbdb83ef13a86b0e63b1 100644
--- a/webrtc/test/testsupport/frame_writer.h
+++ b/webrtc/test/testsupport/frame_writer.h
@@ -15,6 +15,7 @@
 
 #include <string>
 
+#include "webrtc/api/video/video_frame.h"
 #include "webrtc/typedefs.h"
 
 namespace webrtc {
@@ -82,6 +83,20 @@ class Y4mFrameWriterImpl : public YuvFrameWriterImpl {
   const int frame_rate_;
 };
 
+// LibJpeg is not available on iOS
+#if !defined(is_ios)
+class JpegFrameWriter {
+ public:
+  JpegFrameWriter(std::string output_filename);
+  bool WriteFrame(const VideoFrame& input_frame, int quality);
+
+ private:
+  bool frame_written_;
+  const std::string output_filename_;
+  FILE* output_file_;
+};
+#endif
+
 }  // namespace test
 }  // namespace webrtc