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

webrtc/test/frame_generator.h

Index: webrtc/test/frame_generator.h
diff --git a/webrtc/test/frame_generator.h b/webrtc/test/frame_generator.h
index 6b0137df241c0629c6e4e3f8167ceb25f9572925..dfe35b832e7baa1f324db0f7dbb1cf899b8899ee 100644
--- a/webrtc/test/frame_generator.h
+++ b/webrtc/test/frame_generator.h
@@ -89,6 +89,11 @@ class FrameGenerator {
       size_t target_height,
       int64_t scroll_time_ms,
       int64_t pause_time_ms);
+
+  // Creates a frame generator that produces randomly generated slides.
+  // frame_repeat_count determines how many times each slide is shown.
+  static std::unique_ptr<FrameGenerator> CreateSlideGenerator(
+      int width, int height, int frame_repeat_count);
 };
 }  // namespace test
 }  // namespace webrtc