Revert "Roll NDK to r11c and extract it into its own repository."

I reverted the roll in chromium and may not get a chance to attempt to
reland it before someone needs to make a change to this repository.

This reverts commit 04c2c06fe3ef3d93343feb6e83cd932725740d7f.

Change-Id: Ic040bd4b7bb397f7c822cdb78866c7ea270bc3f4
Reviewed-on: https://chromium-review.googlesource.com/350482
Reviewed-by: John Budorick <jbudorick@chromium.org>
Tested-by: John Budorick <jbudorick@chromium.org>