Let Opus increase complexity for low bitrates

webrtc/modules/audio_coding/BUILD.gn

Index: webrtc/modules/audio_coding/BUILD.gn
diff --git a/webrtc/modules/audio_coding/BUILD.gn b/webrtc/modules/audio_coding/BUILD.gn
index f6188a0425742dcbbb67b60190aebcc6f135dc14..0e78abfea65ef47a1985a0223e05bccbd5c6e376 100644
--- a/webrtc/modules/audio_coding/BUILD.gn
+++ b/webrtc/modules/audio_coding/BUILD.gn
@@ -711,10 +711,17 @@ rtc_static_library("webrtc_opus") {
     "../../base:rtc_base_approved",
   ]
 
+  defines = []
+
   if (rtc_build_opus) {
     public_deps = [
       rtc_opus_dir,
     ]
+    if (rtc_opus_variable_complexity) {
+      defines += [ "WEBRTC_OPUS_VARIABLE_COMPLEXITY=1" ]
+    } else {
+      defines += [ "WEBRTC_OPUS_VARIABLE_COMPLEXITY=0" ]
+    }
   } else if (build_with_mozilla) {
     include_dirs = [ getenv("DIST") + "/include/opus" ]
   }