Add APK targets to build libjingle tests for Android.

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 d098ea1d91578fce78220b5ecbb488b8b5626660..7417ced39d151255a070f888c250718143a30f19 100644
--- a/webrtc/system_wrappers/include/field_trial_default.h
+++ b/webrtc/system_wrappers/include/field_trial_default.h
@@ -20,6 +20,8 @@ namespace field_trial {
 // Note: trials_string must never be destroyed.
 void InitFieldTrialsFromString(const char* trials_string);
 
+const char* GetFieldTrialString();
+
 }  // namespace field_trial
 }  // namespace webrtc