Replace a DCHECK with static_assert

This requires marking a bunch of compile-time constants "constexpr"
instead of just "const".

Review-Url: https://codereview.webrtc.org/2335483003
Cr-Commit-Position: refs/heads/master@{#14199}
diff --git a/webrtc/modules/audio_processing/include/audio_processing.h b/webrtc/modules/audio_processing/include/audio_processing.h
index 035fa32..172da08 100644
--- a/webrtc/modules/audio_processing/include/audio_processing.h
+++ b/webrtc/modules/audio_processing/include/audio_processing.h
@@ -513,9 +513,15 @@
     kSampleRate48kHz = 48000
   };
 
-  static const int kNativeSampleRatesHz[];
-  static const size_t kNumNativeSampleRates;
-  static const int kMaxNativeSampleRateHz;
+  // TODO(kwiberg): We currently need to support a compiler (Visual C++) that
+  // complains if we don't explicitly state the size of the array here. Remove
+  // the size when that's no longer the case.
+  static constexpr int kNativeSampleRatesHz[4] = {
+      kSampleRate8kHz, kSampleRate16kHz, kSampleRate32kHz, kSampleRate48kHz};
+  static constexpr size_t kNumNativeSampleRates =
+      arraysize(kNativeSampleRatesHz);
+  static constexpr int kMaxNativeSampleRateHz =
+      kNativeSampleRatesHz[kNumNativeSampleRates - 1];
 
   static const int kChunkSizeMs = 10;
 };