Replace test::Statistics by webrtc::RunningStatistics.

The former became redundant and didn't guarantee
numerical stability for variance computation.

Bug: webrtc:10412
Change-Id: Idc291abe9add41bde9e7734f179e5d6c65f2630b
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/132460
Commit-Queue: Yves Gerey <yvesg@google.com>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27605}
diff --git a/video/BUILD.gn b/video/BUILD.gn
index fffd582..907a96d 100644
--- a/video/BUILD.gn
+++ b/video/BUILD.gn
@@ -274,6 +274,7 @@
       "../modules/video_coding:webrtc_vp9",
       "../rtc_base:rtc_base_approved",
       "../rtc_base:rtc_base_tests_utils",
+      "../rtc_base:rtc_numerics",
       "../system_wrappers",
       "../test:fake_video_codecs",
       "../test:fileutils",