Enabling 'gn check' on webrtc/sdk

webrtc/sdk/objc/Framework/Classes/RTCFieldTrials.mm

Index: webrtc/sdk/objc/Framework/Classes/RTCFieldTrials.mm
diff --git a/webrtc/sdk/objc/Framework/Classes/RTCFieldTrials.mm b/webrtc/sdk/objc/Framework/Classes/RTCFieldTrials.mm
index 5e1ee0afc186337dbc490720ad0e0cb5cf82618f..28ce5414bd9fdd8ec9f92c471db071e0713cc9e2 100644
--- a/webrtc/sdk/objc/Framework/Classes/RTCFieldTrials.mm
+++ b/webrtc/sdk/objc/Framework/Classes/RTCFieldTrials.mm
@@ -14,7 +14,10 @@
 
 #import "WebRTC/RTCLogging.h"
 
-#include "webrtc/system_wrappers/include/field_trial_default.h"
+// Adding 'nogncheck' to disable the gn include headers check.
+// We don't want to depend on 'system_wrappers:field_trial_default' because
+// clients should be able to provide their own implementation.
+#include "webrtc/system_wrappers/include/field_trial_default.h"  // nogncheck
 
 NSString * const kRTCFieldTrialAudioSendSideBweKey = @"WebRTC-Audio-SendSideBwe";
 NSString * const kRTCFieldTrialSendSideBweWithOverheadKey = @"WebRTC-SendSideBwe-WithOverhead";