Rename RTC_HISTOGRAM_* macros to RTC_HISTOGRAM_*_SPARSE_* to indicate that these are for infrequent updates.

This implementation will be replaced by a faster one and sparse will be removed.

BUG=webrtc:5283

Review URL: https://codereview.webrtc.org/1530913002

Cr-Commit-Position: refs/heads/master@{#11099}
diff --git a/webrtc/modules/video_coding/timing.cc b/webrtc/modules/video_coding/timing.cc
index f1a127a..d2563a4 100644
--- a/webrtc/modules/video_coding/timing.cc
+++ b/webrtc/modules/video_coding/timing.cc
@@ -62,14 +62,16 @@
   if (elapsed_sec < metrics::kMinRunTimeInSeconds) {
     return;
   }
-  RTC_HISTOGRAM_COUNTS_100("WebRTC.Video.DecodedFramesPerSecond",
+  RTC_HISTOGRAM_COUNTS_SPARSE_100(
+      "WebRTC.Video.DecodedFramesPerSecond",
       static_cast<int>((num_decoded_frames_ / elapsed_sec) + 0.5f));
-  RTC_HISTOGRAM_PERCENTAGE("WebRTC.Video.DelayedFramesToRenderer",
+  RTC_HISTOGRAM_PERCENTAGE_SPARSE(
+      "WebRTC.Video.DelayedFramesToRenderer",
       num_delayed_decoded_frames_ * 100 / num_decoded_frames_);
   if (num_delayed_decoded_frames_ > 0) {
-    RTC_HISTOGRAM_COUNTS_1000(
+    RTC_HISTOGRAM_COUNTS_SPARSE_1000(
         "WebRTC.Video.DelayedFramesToRenderer_AvgDelayInMs",
-            sum_missed_render_deadline_ms_ / num_delayed_decoded_frames_);
+        sum_missed_render_deadline_ms_ / num_delayed_decoded_frames_);
   }
 }