Enable browser encoding autodetection test

Another attempt to enable the autodetection test that has been
disabled up to now. The new autodetection lib hopefully contributed
to the stability.

Removed Java-side AutodetectionTest since it is essentially a duplicated test
with only a subset of the test documents. With this removal,
WebContents interface getEncoding() can be removed too.

Notes on autodetection result:

gb18030 is detected as GBK. This is acceptable because gb18030
is a superset of GBK, and the test document doesn't contain chars
that appear only is gb18030.

ISO-8859-8-I -> windows-1255. This is also acceptable. See
https://goo.gl/bX0nxa for reference.

The test documents updated to reflect the change above are of non-UTF-8
which is not handled very well by Rietveld. Will land it manually.

BUG=597488
R=dtrainor@chromium.org, jshin@chromium.org, phajdan.jr@chromium.org, thestig@chromium.org

Review URL: https://codereview.chromium.org/2294173002 .

Cr-Commit-Position: refs/heads/master@{#416120}
9 files changed