Merge "libui: improve Region::validate"

bool Region::validate(const Region& reg, const char* name, bool silent)

{

    if (reg.mStorage.isEmpty()) {

        ALOGE_IF(!silent, "%s: mStorage is empty, which is never valid", name);

        // return immediately as the code below assumes mStorage is non-empty

        return false;

    }

    bool result = true;

    const_iterator cur = reg.begin();

    const_iterator const tail = reg.end();