Remove deprecated hidden public methods from InputMethodUtils.

This is a follow up CL for a recent attempt to minimize
the number of default enabled IMEs.
- part1: I831502db502f4073c9c2f50ce7705a4e45e2e1e3
- part2: Ife93d909fb8a24471c425c903e2b7048826e17a3
- part3: I6571d464a46453934f0a8f5e79018a67a9a3c845
- part4: I871ccda787eb0f1099ba3574356c1da4b33681f3

This CL removes following deprecated hidden public methods
from InputMethodUtils as planned.
- isSystemImeThatHasEnglishKeyboardSubtype(InputMethodInfo)
- isValidSystemDefaultIme(boolean, InputMethodInfo, Context)
- containsSubtypeOf(InputMethodInfo, String, String)

This is a pure code refactoring with preserving the current
logic. Hence no behavior change is intended.

Change-Id: I1ff994cbbdef83e1e907a0d88aa9ae09d45263b4
diff --git a/services/core/java/com/android/server/InputMethodManagerService.java b/services/core/java/com/android/server/InputMethodManagerService.java
index 4d0868a..9ec886c 100644
--- a/services/core/java/com/android/server/InputMethodManagerService.java
+++ b/services/core/java/com/android/server/InputMethodManagerService.java
@@ -764,9 +764,11 @@
 
         InputMethodInfo defIm = null;
         for (InputMethodInfo imi : mMethodList) {
-            if (defIm == null) {
-                if (InputMethodUtils.isValidSystemDefaultIme(
-                        mSystemReady, imi, context)) {
+            if (defIm == null && mSystemReady) {
+                final Locale systemLocale = context.getResources().getConfiguration().locale;
+                if (InputMethodUtils.isSystemImeThatHasSubtypeOf(imi, context,
+                        true /* checkDefaultAttribute */, systemLocale, false /* checkCountry */,
+                        InputMethodUtils.SUBTYPE_MODE_ANY)) {
                     defIm = imi;
                     Slog.i(TAG, "Selected default: " + imi.getId());
                 }