Fix a bug for counting code points in WordComposer.java

This bug threw an ArrayIndexOutOfBoundsException when the word length
is 49 (maxSize + 1) when calling StringUtils.copyCodePointsAndReturnCodePointCount(...)
in the same function. This bug is discovered by running SKETCH.

The intent is to count the code points from index 0 to index i (included).
The original code only counted the code points from index 0 to index (i-1).

Bug: 13969542
Change-Id: Idbf596aba2379ba552dbe580c83c42044d505aaf