Move most of TestNaClBrowserDelegate to another file.

Move most of TestNaClBrowserDelegate to another file.

It was originally in nacl_file_host_unittest.
Move it to components/ and consider it the "base" test
version. In nacl_file_host_unittest, provide slimmer version
that overrides just what we need for the unittest.

This means that we can reuse the TestNaClBrowserDelegate for
other tests. E.g., I'll be adding one for checking that
the "abi-version" matters for translation caching, and
to test that we need to do a similar trick of having a
Get/SetPnaclDirectory pair, so as not to modify the PNaCl
files inline.

It also means that we don't need to modify the test file
every time something is added to the NaClBrowserDelegate.

BUG=none
NOTRY=true
(already tried)

Review URL: https://codereview.chromium.org/51323004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233404 0039d316-1c4b-4281-b951-d872f2087c98