A stub of sparse histogram factory getter is added so that Chromium can
provide an implementation using base::SparseHistogram for the metrics
macro RTC_HISTOGRAM_ENUMERATION_SPARSE. The default implementation in
WebRTC reuses the non-sparse version.
Bug: None
Change-Id: Ia091ca7aaacb6baa92027cd99d821bbc8da8d780
Reviewed-on: https://webrtc-review.googlesource.com/85740
Reviewed-by: Tommi <tommi@webrtc.org>
Commit-Queue: Qingsi Wang <qingsi@google.com>
Cr-Commit-Position: refs/heads/master@{#23750}