Create Espresso test for WifiSettings.

This method was being stripped by proguard and hence the tests could not
run.

Bug: b/36403696
Test:  runtest --path
packages/apps/Settings/tests/app/src/com/android/settings/wifi/WifiSettingsUiTest.java

Change-Id: I30b26e960a876c0c024154bee809c0ab6e988e39
diff --git a/packages/SettingsLib/Android.mk b/packages/SettingsLib/Android.mk
index 67ef40a..1ad4fea 100644
--- a/packages/SettingsLib/Android.mk
+++ b/packages/SettingsLib/Android.mk
@@ -6,6 +6,7 @@
 LOCAL_MODULE := SettingsLib
 
 LOCAL_SHARED_ANDROID_LIBRARIES := \
+    android-support-annotations \
     android-support-v4 \
     android-support-v7-recyclerview \
     android-support-v7-preference \