Convert nacl_loader_unittests to run exclusively on Swarming

Convert nacl_loader_unittests to run exclusively on Swarming

Remove apparently unused stuff from the existing isolate file
and make it work on Mac and Windows.

0 configs already ran on Swarming
24 used to run locally and were converted:
- chromium.chromiumos.json: Linux ChromiumOS Ozone Tests (1)
- chromium.chromiumos.json: Linux ChromiumOS Tests (1)
- chromium.chromiumos.json: Linux ChromiumOS Tests (dbg)(1)
- chromium.fyi.json: ClangToTLinux tester
- chromium.fyi.json: Linux Trusty
- chromium.fyi.json: Linux Trusty (dbg)
- chromium.linux.json: Linux Tests
- chromium.linux.json: Linux Tests (dbg)(1)
- chromium.linux.json: Linux Tests (dbg)(1)(32)
- chromium.mac.json: Mac10.10 Tests
- chromium.mac.json: Mac10.6 Tests
- chromium.mac.json: Mac10.8 Tests
- chromium.mac.json: Mac10.9 Tests
- chromium.mac.json: Mac10.9 Tests (dbg)
- chromium.memory.fyi.json: Linux ChromeOS MSan Tests
- chromium.memory.fyi.json: Linux MSan Tests
- chromium.memory.json: Linux Chromium OS ASan LSan Tests (1)
- chromium.webkit.json: Linux ChromiumOS Tests (1)
- chromium.webkit.json: Linux ChromiumOS Tests (dbg)(1)
- chromium.win.json: Vista Tests (1)
- chromium.win.json: Win 7 Tests x64 (1)
- chromium.win.json: Win7 Tests (1)
- chromium.win.json: Win7 Tests (dbg)(1)
- chromium.win.json: XP Tests (1)

Ran:
  ./manage.py --convert nacl_loader_unittests

BUG=98637

Review URL: https://codereview.chromium.org/1209213003

Cr-Commit-Position: refs/heads/master@{#337314}