APM: Change 3 UMA metrics to fewer but linearly distributed buckets

webrtc/modules/audio_processing/agc/agc_manager_direct.cc

Index: webrtc/modules/audio_processing/agc/agc_manager_direct.cc
diff --git a/webrtc/modules/audio_processing/agc/agc_manager_direct.cc b/webrtc/modules/audio_processing/agc/agc_manager_direct.cc
index f8fc310c57569aa28dab3a1d440bcc09292f72e7..576bf2d56a7d3f9921cb5df78579bf6764203e29 100644
--- a/webrtc/modules/audio_processing/agc/agc_manager_direct.cc
+++ b/webrtc/modules/audio_processing/agc/agc_manager_direct.cc
@@ -411,7 +411,8 @@ void AgcManagerDirect::UpdateGain() {
   SetLevel(LevelFromGainError(residual_gain, level_));
   if (old_level != level_) {
     // level_ was updated by SetLevel; log the new value.
-    RTC_HISTOGRAM_ENUMERATION("WebRTC.Audio.AgcLevel", level_, kMaxMicLevel);
+    RTC_HISTOGRAM_COUNTS_LINEAR("WebRTC.Audio.AgcSetLevel", level_, 1,
+                                kMaxMicLevel, 50);
   }
 }