Fix unit tests by adding @UsedForTesting.

Change-Id: I62ec07210817295f59a174383ee4b33cc4fc2ca6

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

@@ -362,6 +362,7 @@ abstract public class ExpandableBinaryDictionary extends Dictionary {
     /**
      * Dynamically remove the n-gram entry in the dictionary.
      */
+    @UsedForTesting
     public void removeNgramDynamically(final PrevWordsInfo prevWordsInfo, final String word) {
         reloadDictionaryIfRequired();
         asyncExecuteTaskWithWriteLock(new Runnable() {