Demote skipped characters matched words with respect to length.

Words that matched user input with skipped characters used to be demoted
in BinaryDictionary by a constant factor and not at all in those dictionaries
implemented in java code. To represent the fact that the impact of a skipped
character gets larger as the word is shorter, this change will implement a
demotion that gets larger as the typed word is shorter. The demotion rate
is (n - 2) / (n - 1) where n is the length of the typed word for n >= 2.
It implements it for both BinaryDictionary and java dictionaries.

Bug: 3340731
Change-Id: I3a18be80a9708981d56a950dc25fe08f018b5b89
diff --git a/native/src/unigram_dictionary.h b/native/src/unigram_dictionary.h
index a959845..2912cb0 100644
--- a/native/src/unigram_dictionary.h
+++ b/native/src/unigram_dictionary.h
@@ -71,7 +71,8 @@
             const int nextLettersSize);
     void registerNextLetter(unsigned short c, int *nextLetters, int nextLettersSize);
     int calculateFinalFreq(const int inputIndex, const int depth, const int snr, const int skipPos,
-            const int excessivePos, const int transposedPos, const int freq, const bool sameLength);
+            const int excessivePos, const int transposedPos, const int freq,
+            const bool sameLength) const;
     void onTerminalWhenUserTypedLengthIsGreaterThanInputLength(unsigned short *word,
             const int inputIndex, const int depth, const int snr, int *nextLetters,
             const int nextLettersSize, const int skipPos, const int excessivePos,
@@ -95,8 +96,8 @@
     bool processCurrentNodeForExactMatch(const int firstChildPos,
             const int startInputIndex, const int depth, unsigned short *word,
             int *newChildPosition, int *newCount, bool *newTerminal, int *newFreq, int *siblingPos);
-    bool existsAdjacentProximityChars(const int inputIndex, const int inputLength);
-    inline const int* getInputCharsAt(const int index) {
+    bool existsAdjacentProximityChars(const int inputIndex, const int inputLength) const;
+    inline const int* getInputCharsAt(const int index) const {
         return mInputCodes + (index * MAX_PROXIMITY_CHARS);
     }
     const unsigned char *DICT;