Make LocaleList constructor non-nullable

This commit makes the LocaleList constructor require non-null
arguments in all cases, and fixes all uses of LocaleList that could
previously pass a null to use getEmptyLocaleList() instead (which is
preferred anyway becaues it avoids an allocation.

Bug: 28460668
Change-Id: I4b8b3cfa82914412731c2b79003951c46cb2afa1

core/java/android/content/res/Configuration.java

@@ -744,7 +744,7 @@ public final class Configuration implements Parcelable, Comparable<Configuration
     private void fixUpLocaleList() {
         if ((locale == null && !mLocaleList.isEmpty()) ||
                 (locale != null && !locale.equals(mLocaleList.get(0)))) {
-            mLocaleList = new LocaleList(locale);
+            mLocaleList = locale == null ? LocaleList.getEmptyLocaleList() : new LocaleList(locale);
         }
     }
 
@@ -1481,7 +1481,7 @@ public final class Configuration implements Parcelable, Comparable<Configuration
      * @param loc The locale. Can be null.
      */
     public void setLocale(@Nullable Locale loc) {
-        setLocales(new LocaleList(loc));
+        setLocales(loc == null ? LocaleList.getEmptyLocaleList() : new LocaleList(loc));
     }
 
     /**

core/java/android/text/style/LocaleSpan.java

@@ -50,7 +50,7 @@ public class LocaleSpan extends MetricAffectingSpan implements ParcelableSpan {
      * @see #LocaleSpan(LocaleList)
      */
     public LocaleSpan(@Nullable Locale locale) {
-        mLocales = new LocaleList(locale);
+        mLocales = locale == null ? LocaleList.getEmptyLocaleList() : new LocaleList(locale);
     }
 
     /**

core/java/android/util/LocaleList.java

@@ -169,8 +169,8 @@ public final class LocaleList implements Parcelable {
      * @throws NullPointerException if any of the input locales is <code>null</code>.
      * @throws IllegalArgumentException if any of the input locales repeat.
      */
-    public LocaleList(@Nullable Locale... list) {
-        if (list == null || list.length == 0) {
+    public LocaleList(@NonNull Locale... list) {
+        if (list.length == 0) {
             mList = sEmptyList;
             mStringRepresentation = "";
         } else {