Add chrome/browser/loader to content_loader WATCHLIST.

It isn't actually in content, but it's very closely related to
content/browser/loader, and small enough that it doesn't seem worth its
own list.

BUG=none

Review-Url: https://codereview.chromium.org/2354993002
Cr-Commit-Position: refs/heads/master@{#420860}

WATCHLISTS

@@ -336,7 +336,8 @@
       'filepath': 'content/.*bluetooth'
     },
     'content_loader': {
-      'filepath': 'content/browser/loader|'\
+      'filepath': 'chrome/browser/loader|' \
+                  'content/browser/loader|' \
                   'content/child/*loader',
     },
     'content_renderer': {