Bug 1405404: Add 'de' to list of pocket whitelisted locales. r=liuche

This is used in multi-locale builds, e.g. [1] where all German is "de" but in
[2], we have a separate l10n repo for en-GB.

[1]: https://hg.mozilla.org/releases/l10n/mozilla-beta/de
[2]: https://hg.mozilla.org/releases/l10n/mozilla-beta/en-GB

MozReview-Commit-ID: CXw9aFH9psz

--HG--
extra : rebase_source : 3f92c5f3cbefbb7cea14a1f673edce546a640a96

mobile/android/base/java/org/mozilla/gecko/activitystream/homepanel/ActivityStreamConfiguration.java

@@ -22,8 +22,16 @@ import java.util.Set;
 public class ActivityStreamConfiguration {
 
     private static final Set<Locale> pocketEnabledLocales;
+
+    /**
+     * Notes for testing: Firefox for Android can get its locale from two places: the system locale and an override for
+     * this locale specified in Fennec settings. As such, you should be sure to test all locale updates with both
+     * settings when possible. For example, Deutsch will be "de-DE" in the Android system but "de" when using the Fennec
+     * override.
+     */
     @VisibleForTesting static final String[] pocketEnabledLocaleTags = new String[] {
             // Sorted alphabetically to preserve blame for additions/removals.
+            "de", // used by Firefox multi-locale builds.
             "de-AT",
             "de-CH",
             "de-DE",

mobile/android/tests/background/junit4/src/org/mozilla/gecko/activitystream/homepanel/TestActivityStreamConfiguration.java

@@ -58,6 +58,10 @@ public class TestActivityStreamConfiguration {
      */
     private Locale getLocaleFromLanguageTag(final String tag) {
         final String[] split = tag.split("-");
-        return new Locale(split[0], split[1]);
+        if (split.length == 1) {
+            return new Locale(split[0]);
+        } else {
+            return new Locale(split[0], split[1]);
+        }
     }
 }