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

webrtc/modules/audio_processing/agc/agc_manager_direct.cc

 /*
  *  Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 393 matching lines @@
   LOG(LS_INFO) << "[agc] rms_error=" << rms_error << ", "
                << "target_compression=" << target_compression_ << ", "
                << "residual_gain=" << residual_gain;
   if (residual_gain == 0)
     return;
 
   int old_level = level_;
   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);
   }
 }
 
 void AgcManagerDirect::UpdateCompressor() {
   if (compression_ == target_compression_) {
     return;
   }
 
   // Adapt the compression gain slowly towards the target, in order to avoid
   // highly perceptible changes.
@@ skipping 18 matching lines @@
     compression_ = new_compression;
     compression_accumulator_ = new_compression;
     if (gctrl_->set_compression_gain_db(compression_) != 0) {
       LOG(LS_ERROR) << "set_compression_gain_db(" << compression_
                     << ") failed.";
     }
   }
 }
 
 }  // namespace webrtc