[chrome.displaySource] Implement LPCM audio encoder.

extensions/renderer/api/display_source/wifi_display/wifi_display_audio_encoder.h

Index: extensions/renderer/api/display_source/wifi_display/wifi_display_audio_encoder.h
diff --git a/extensions/renderer/api/display_source/wifi_display/wifi_display_audio_encoder.h b/extensions/renderer/api/display_source/wifi_display/wifi_display_audio_encoder.h
index 2c0f6dd537382cb6a11761d1e16bfc18ecc3dbfe..51c7aa732782388a17573277fbba3137593d1671 100644
--- a/extensions/renderer/api/display_source/wifi_display/wifi_display_audio_encoder.h
+++ b/extensions/renderer/api/display_source/wifi_display/wifi_display_audio_encoder.h
@@ -26,6 +26,11 @@ class WiFiDisplayAudioEncoder : public WiFiDisplayMediaEncoder,
  protected:
   static const size_t kInvalidCodecModeValue = ~static_cast<size_t>(0u);
 
+  // A factory method that creates a new encoder instance for Linear Pulse-Code
+  // Modulation (LPCM) audio encoding.
+  static void CreateLPCM(const wds::AudioCodec& audio_codec,
+                         const AudioEncoderCallback& encoder_callback);
+
   explicit WiFiDisplayAudioEncoder(const wds::AudioCodec& audio_codec);
   ~WiFiDisplayAudioEncoder() override;