Convert webkit_unit_tests to run exclusively on Swarming

Convert webkit_unit_tests to run exclusively on Swarming

0 configs already ran on Swarming
43 used to run locally and were converted:
- chromium.fyi.json: ClangToTLinux tester
- chromium.fyi.json: ClangToTLinuxASan tester
- chromium.fyi.json: ClangToTMac tester
- chromium.fyi.json: ClangToTMacASan tester
- chromium.fyi.json: ClangToTWin tester
- chromium.fyi.json: ClangToTWin(dbg) tester
- chromium.fyi.json: ClangToTWin(dll) tester
- chromium.fyi.json: ClangToTWin64 tester
- chromium.fyi.json: ClangToTWin64(dbg) tester
- chromium.fyi.json: ClangToTWin64(dll) tester
- chromium.fyi.json: CrWinClang tester
- chromium.fyi.json: CrWinClang(dbg) tester
- chromium.fyi.json: CrWinClang(shared) tester
- chromium.fyi.json: CrWinClang64 tester
- chromium.fyi.json: CrWinClang64(dbg) tester
- chromium.fyi.json: CrWinClang64(dll) tester
- chromium.fyi.json: CrWinClangLLD tester
- chromium.webkit.json: WebKit Linux
- chromium.webkit.json: WebKit Linux (dbg)
- chromium.webkit.json: WebKit Linux 32
- chromium.webkit.json: WebKit Linux Leak
- chromium.webkit.json: WebKit Linux Oilpan
- chromium.webkit.json: WebKit Linux Oilpan (dbg)
- chromium.webkit.json: WebKit Linux Oilpan Leak
- chromium.webkit.json: WebKit Linux Trusty
- chromium.webkit.json: WebKit Mac Oilpan
- chromium.webkit.json: WebKit Mac Oilpan (dbg)
- chromium.webkit.json: WebKit Mac10.10
- chromium.webkit.json: WebKit Mac10.6
- chromium.webkit.json: WebKit Mac10.6 (dbg)
- chromium.webkit.json: WebKit Mac10.7
- chromium.webkit.json: WebKit Mac10.7 (dbg)
- chromium.webkit.json: WebKit Mac10.8
- chromium.webkit.json: WebKit Mac10.9
- chromium.webkit.json: WebKit Mac10.9 (retina)
- chromium.webkit.json: WebKit Win Oilpan
- chromium.webkit.json: WebKit Win Oilpan (dbg)
- chromium.webkit.json: WebKit Win x64 Builder
- chromium.webkit.json: WebKit Win x64 Builder (dbg)
- chromium.webkit.json: WebKit Win10
- chromium.webkit.json: WebKit Win7
- chromium.webkit.json: WebKit Win7 (dbg)
- chromium.webkit.json: WebKit XP

Ran:
  ./manage.py --convert webkit_unit_tests

R=maruel@chromium.org,dpranke@chromium.org
BUG=98637,524758

Review URL: https://codereview.chromium.org/1341903002

Cr-Commit-Position: refs/heads/master@{#348834}