Use translation of fallback umlauts digraphs for German.

For German : handle "ae", "oe" and "ue" to be alternate forms for
umlaut-bearing versions of "a", "o" and "u".

Issue: 3275926

Change-Id: I056c707cdacc464ceab63be56c016c7f8439196c
diff --git a/java/res/xml/method.xml b/java/res/xml/method.xml
index b1f7379..8dec7ab 100644
--- a/java/res/xml/method.xml
+++ b/java/res/xml/method.xml
@@ -65,6 +65,7 @@
             android:label="@string/subtype_mode_de_keyboard"
             android:imeSubtypeLocale="de"
             android:imeSubtypeMode="keyboard"
+            android:imeSubtypeExtraValue="requiresGermanUmlautProcessing"
     />
     <subtype android:icon="@drawable/ic_subtype_mic"
             android:label="@string/subtype_mode_de_voice"