Merge "Refactor key preview code"

...rc/com/android/inputmethod/keyboard/KeyboardSwitcher.java

java/src/com/android/inputmethod/keyboard/KeyboardView.java

...c/com/android/inputmethod/keyboard/LatinKeyboardView.java

.../src/com/android/inputmethod/keyboard/PointerTracker.java

...com/android/inputmethod/keyboard/PointerTrackerQueue.java

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