Manually add SignalStrength to preloaded-classes

Bug: 19323020
Change-Id: I61e9d2dd5d06fe2353da17e5646f259122e5ea98
diff --git a/preloaded-classes b/preloaded-classes
index dee84f0..c8d8c5d 100644
--- a/preloaded-classes
+++ b/preloaded-classes
@@ -1172,6 +1172,7 @@
 android.telecom.InCallService
 android.telephony.PhoneNumberUtils
 android.telephony.Rlog
+android.telephony.SignalStrength
 android.telephony.SubscriptionManager
 android.telephony.TelephonyManager
 android.text.AndroidBidi