WebRTC AGC2 flags: replace deprecated fields.

Bug: webrtc:7494
Change-Id: I0cdcf1ac0bb0726913a4fdd15fcdaa324c4e86b7
Reviewed-on: https://chromium-review.googlesource.com/c/1335488Reviewed-by: Max Morin <maxmorin@chromium.org>
Commit-Queue: Ale Bzk <alessiob@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608297}

media/webrtc/audio_processor.cc

@@ -312,7 +312,7 @@ void AudioProcessor::InitializeAPM() {
     apm_config.gain_controller2.enabled =
         settings_.automatic_gain_control ==
         AutomaticGainControlType::kHybridExperimental;
-    apm_config.gain_controller2.fixed_gain_db = 0.f;
+    apm_config.gain_controller2.fixed_digital.gain_db = 0.f;
   }
 
   audio_processing_->ApplyConfig(apm_config);