Android: moves base_unittests_jni_headers to use long for JNI.

BUG=317523

Review URL: https://codereview.chromium.org/131523002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243908 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 243908