[HW7.5] Introduce the @Nonnull annotation (take 2)

java/Android.mk

java/src/com/android/inputmethod/event/Combiner.java

java/src/com/android/inputmethod/event/CombinerChain.java

java/src/com/android/inputmethod/event/DeadKeyCombiner.java

.../src/com/android/inputmethod/event/MyanmarReordering.java

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

tools/dicttool/Android.mk