Add CHECKs for file descriptors used in select() by InotifyReaderTask

Since these are used in an fd_set, there's the possibility that invalid file descriptors cause stack overflow/corruption.

BUG=chromium:105162
TEST=No functional changes, compiles and passes tests.


Review URL: http://codereview.chromium.org/8681006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@111369 0039d316-1c4b-4281-b951-d872f2087c98
FilePathWatcherImpl::FilePathWatcherImpl()
    : delegate_(NULL) {
}

FilePathWatcherImpl::FilePathWatcherImpl()
    : delegate_(NULL) {
}
