move_blink_source.py: Update _PATH_RULES_SPECIFIER in check-webkit-style.

It is a list of exceptional rules, and contains some Source/ paths.

Bug: 578345
Change-Id: I17e65d35c4809b9c91217db086e1af10d82dea54
Reviewed-on: https://chromium-review.googlesource.com/974605
Commit-Queue: Kent Tamura <tkent@chromium.org>
Reviewed-by: Quinten Yearsley <qyearsley@chromium.org>
Cr-Commit-Position: refs/heads/master@{#544991}

third_party/blink/tools/move_blink_source.py

@@ -163,6 +163,8 @@ class MoveBlinkSource(object):
             ('third_party/WebKit/Tools/Scripts/audit-non-blink-usage.py',
              [('third_party/WebKit/Source', 'third_party/blink/renderer'),
               ('ls-files third_party/WebKit', 'ls-files third_party/blink')]),
+            ('third_party/WebKit/Tools/Scripts/webkitpy/style/checker.py',
+             [('Source/', 'renderer/')]),
             ('third_party/WebKit/public/BUILD.gn',
              [('$root_gen_dir/third_party/WebKit',
                '$root_gen_dir/third_party/blink')]),