Execute the switching to a different IME in a POOL_EXECUTOR.

Using only a single thread may slow down the application, if there is already another thread running.

Bug: 5142142
Change-Id: I314480a58af20ea09458ff82e586304fc3c7c070

java/src/com/android/inputmethod/latin/SubtypeSwitcher.java

@@ -318,7 +318,7 @@ public class SubtypeSwitcher {
                 // when the API level is 10 or previous.
                 mService.notifyOnCurrentInputMethodSubtypeChanged(subtype);
             }
-        }.execute();
+        }.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
     }
 
     public Drawable getShortcutIcon() {