Broke out 'level_indicator' of the voice_engine GN target.

webrtc/voice_engine/BUILD.gn

Index: webrtc/voice_engine/BUILD.gn
diff --git a/webrtc/voice_engine/BUILD.gn b/webrtc/voice_engine/BUILD.gn
index b587d04073fb778585174cb4a694a45bd0440da5..808d980c6f475685a9b4c10948cbf6f64d6ad301 100644
--- a/webrtc/voice_engine/BUILD.gn
+++ b/webrtc/voice_engine/BUILD.gn
@@ -29,8 +29,6 @@ source_set("voice_engine") {
     "include/voe_rtp_rtcp.h",
     "include/voe_video_sync.h",
     "include/voe_volume_control.h",
-    "level_indicator.cc",
-    "level_indicator.h",
     "monitor_module.cc",
     "monitor_module.h",
     "network_predictor.cc",
@@ -91,6 +89,7 @@ source_set("voice_engine") {
   }
 
   deps = [
+    ":level_indicator",
     "..:rtc_event_log",
     "..:webrtc_common",
     "../base:rtc_base_approved",
@@ -108,6 +107,22 @@ source_set("voice_engine") {
   ]
 }
 
+source_set("level_indicator") {
+  sources = [
+    "level_indicator.cc",
+    "level_indicator.h",
+  ]
+
+  configs += [ "..:common_config" ]
+  public_configs = [ "..:common_inherited_config" ]
+
+  deps = [
+    "..:webrtc_common",
+    "../base:rtc_base_approved",
+    "../common_audio",
+  ]
+}
+
 if (rtc_include_tests) {
   test("voice_engine_unittests") {
     deps = [