Use constexpr to avoid a static initializer

webrtc/modules/audio_processing/vad/vad_audio_proc.cc

Index: webrtc/modules/audio_processing/vad/vad_audio_proc.cc
diff --git a/webrtc/modules/audio_processing/vad/vad_audio_proc.cc b/webrtc/modules/audio_processing/vad/vad_audio_proc.cc
index af1214b99a04ccce9835f364f2218bd6d57cde60..b9345885978e4f640472182bb624bd346101f25a 100644
--- a/webrtc/modules/audio_processing/vad/vad_audio_proc.cc
+++ b/webrtc/modules/audio_processing/vad/vad_audio_proc.cc
@@ -33,9 +33,9 @@ namespace webrtc {
 struct VadAudioProc::PitchAnalysisStruct : public ::PitchAnalysisStruct {};
 struct VadAudioProc::PreFiltBankstr : public ::PreFiltBankstr {};
 
-static const float kFrequencyResolution =
+static constexpr float kFrequencyResolution =
     kSampleRateHz / static_cast<float>(VadAudioProc::kDftSize);
-static const int kSilenceRms = 5;
+static constexpr int kSilenceRms = 5;
 
 // TODO(turajs): Make a Create or Init for VadAudioProc.
 VadAudioProc::VadAudioProc()