system_wrappers: Fix include header guards.

webrtc/system_wrappers/include/field_trial_default.h

Index: webrtc/system_wrappers/include/field_trial_default.h
diff --git a/webrtc/system_wrappers/include/field_trial_default.h b/webrtc/system_wrappers/include/field_trial_default.h
index fafe550dccbd198d2d811aab3d298afabd7953b0..d098ea1d91578fce78220b5ecbb488b8b5626660 100644
--- a/webrtc/system_wrappers/include/field_trial_default.h
+++ b/webrtc/system_wrappers/include/field_trial_default.h
@@ -8,8 +8,8 @@
 // be found in the AUTHORS file in the root of the source tree.
 //
 
-#ifndef WEBRTC_SYSTEM_WRAPPERS_INTERFACE_FIELD_TRIAL_DEFAULT_H_
-#define WEBRTC_SYSTEM_WRAPPERS_INTERFACE_FIELD_TRIAL_DEFAULT_H_
+#ifndef WEBRTC_SYSTEM_WRAPPERS_INCLUDE_FIELD_TRIAL_DEFAULT_H_
+#define WEBRTC_SYSTEM_WRAPPERS_INCLUDE_FIELD_TRIAL_DEFAULT_H_
 
 namespace webrtc {
 namespace field_trial {
@@ -23,4 +23,4 @@ void InitFieldTrialsFromString(const char* trials_string);
 }  // namespace field_trial
 }  // namespace webrtc
 
-#endif  // WEBRTC_SYSTEM_WRAPPERS_INTERFACE_FIELD_TRIAL_DEFAULT_H_
+#endif  // WEBRTC_SYSTEM_WRAPPERS_INCLUDE_FIELD_TRIAL_DEFAULT_H_