WebRTC AGC2 flags: replace deprecated fields.

Bug: webrtc:7494
Change-Id: I5b69192aa4e1a3eaed9df041334619af857ed640
Reviewed-on: https://chromium-review.googlesource.com/c/1337337Reviewed-by: Max Morin <maxmorin@chromium.org>
Commit-Queue: Ale Bzk <alessiob@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608340}

content/renderer/media/stream/media_stream_audio_processor.cc

@@ -671,7 +671,7 @@ void MediaStreamAudioProcessor::InitializeAudioProcessingModule(
   if (properties.goog_experimental_auto_gain_control) {
     apm_config.gain_controller2.enabled =
         base::FeatureList::IsEnabled(features::kWebRtcHybridAgc);
-    apm_config.gain_controller2.fixed_gain_db = 0.f;
+    apm_config.gain_controller2.fixed_digital.gain_db = 0.f;
   }
   ConfigPreAmplifier(&apm_config, pre_amplifier_fixed_gain_factor);
   audio_processing_->ApplyConfig(apm_config);