Update IDL path in WATCHLIST rule.

Change-Id: I4cacf95b98f3f4dbe17c49f4ae566849cbafc4b1
Reviewed-on: https://chromium-review.googlesource.com/1002658Reviewed-by: Ian Clelland <iclelland@chromium.org>
Commit-Queue: Ian Clelland <iclelland@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550616}

WATCHLISTS

@@ -1383,7 +1383,7 @@
                   '|chromeos/dbus/smb_provider_client',
     },
     'source_idls': {
-      'filepath': 'third_party/Webkit/Source/(core|modules|platform)/.*\.idl',
+      'filepath': 'third_party/blink/renderer/(core|modules|platform)/.*\.idl',
     },
     'spellcheck': {
       'filepath': 'chrome/browser/spellchecker/'\