Make InputFilter.AllCaps constructor reject null locales

In I021ff2a97a60396fb1b6e4940d91d3cd6ccb6196, new API for
InputFilter.AllCaps was added. It accepted null as input. This CL
changes that so null locales would be rejected.

Test: bit CtsTextTestCases:android.text.cts.InputFilter_AllCapsTest
Fixes: 64261334
Bug: 37222101

Change-Id: Ic87942c3f341f71bc3c1c833b52ea3e751461e47

core/java/android/text/InputFilter.java

@@ -16,7 +16,9 @@
 
 package android.text;
 
-import android.annotation.Nullable;
+import android.annotation.NonNull;
+
+import com.android.internal.util.Preconditions;
 
 import java.util.Locale;
 
@@ -64,7 +66,8 @@ public interface InputFilter
          * Constructs a locale-specific AllCaps filter, to make sure capitalization rules of that
          * locale are used for transforming the sequence.
          */
-        public AllCaps(@Nullable Locale locale) {
+        public AllCaps(@NonNull Locale locale) {
+            Preconditions.checkNotNull(locale);
             mLocale = locale;
         }