Move the android library loader from content to base

The android library loader has no logical connection with content. Mojo
shell, which doesn't depend on content, wants to use it. This CL
moves it from content to base.

BUG=225101
NOTRY=true

Review URL: https://codereview.chromium.org/141223002

git-svn-id: http://src.chromium.org/chrome/trunk/src/testing@250113 4ff67af0-8c30-449e-8e8b-ad334ec8d88c