Add a new frame generator that cycles through randomly generated slides.

webrtc/test/frame_generator_capturer.h

Index: webrtc/test/frame_generator_capturer.h
diff --git a/webrtc/test/frame_generator_capturer.h b/webrtc/test/frame_generator_capturer.h
index f62afbac2d998f43cc130839935b27ed43b5d3a0..21fa075a0269628805ec64aa5def4037fdebb6ef 100644
--- a/webrtc/test/frame_generator_capturer.h
+++ b/webrtc/test/frame_generator_capturer.h
@@ -50,6 +50,12 @@ class FrameGeneratorCapturer : public VideoCapturer {
                                                    size_t height,
                                                    int target_fps,
                                                    Clock* clock);
+
+  static FrameGeneratorCapturer* CreateSlideGenerator(size_t width,
+                                                      size_t height,
+                                                      int frame_repeat_count,
+                                                      int target_fps,
+                                                      Clock* clock);
   virtual ~FrameGeneratorCapturer();
 
   void Start() override;