Allow ImeSutype with null languagtag to be passed to IMS

Imesubtypes with null languagtag should be allowed to be set.
If ImeSubtype is null, user can still select a PK layout for it
in the settings and we need the callbacks so that when user
switches to that particular ImeSubtype, we select the user
selected layout.

Test: atest InputMethodSubtypeTest
Bug: 20805588
Change-Id: I8541e6132bdf04245831010f11ceabb651dd34ca

core/java/android/view/inputmethod/InputMethodSubtype.java

@@ -536,14 +536,7 @@ public final class InputMethodSubtype implements Parcelable {
         if (!TextUtils.equals(getMode(), SUBTYPE_MODE_KEYBOARD)) {
             return false;
         }
-        if (isAuxiliary()) {
-            return false;
-        }
-        final String langTag = getCanonicalizedLanguageTag();
-        if (langTag.isEmpty() || TextUtils.equals(langTag, UNDEFINED_LANGUAGE_TAG)) {
-            return false;
-        }
-        return true;
+        return !isAuxiliary();
     }
 
     /**

core/tests/coretests/src/android/view/inputmethod/InputMethodSubtypeTest.java

@@ -176,14 +176,6 @@ public class InputMethodSubtypeTest {
         // Auxiliary subtype not suitable.
         assertFalse(getValidBuilder.get().setIsAuxiliary(true).build()
                 .isSuitableForPhysicalKeyboardLayoutMapping());
-
-        // languageTag == null is not suitable.
-        assertFalse(getValidBuilder.get().setLanguageTag(null).build()
-                .isSuitableForPhysicalKeyboardLayoutMapping());
-
-        // languageTag == "und" is not suitable.
-        assertFalse(getValidBuilder.get().setLanguageTag("und").build()
-                .isSuitableForPhysicalKeyboardLayoutMapping());
     }
 
     private static InputMethodSubtype cloneViaParcel(final InputMethodSubtype original) {