Add 'self' to Zip Archiver script-src content security policy

Fix issues where Files app failed to mount .zip files, and also
failed to zip files in M69 dev.

Cause was on the Zip Archiver extension failing to load its own
JS files due the manifest Content Security Policy (CSP) changes
submitted in issue 836412.

Bug: 864256, 865197, 836412
Change-Id: I8ffd382671deac0a23dfa5688830d9608a919bf5
Reviewed-on: https://chromium-review.googlesource.com/1147893Reviewed-by: Tatsuhisa Yamaguchi <yamaguchi@chromium.org>
Reviewed-by: Noel Gordon <noel@chromium.org>
Commit-Queue: Luciano Pacheco <lucmult@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577438}

chrome/browser/resources/chromeos/zip_archiver/manifest.json

@@ -68,6 +68,6 @@
         "js/volume.js"
       ]
     },
-    "content_security_policy": "default-src 'none'; script-src chrome://resources; style-src 'unsafe-inline' chrome://resources;"
+    "content_security_policy": "default-src 'none'; script-src 'self' chrome://resources; style-src 'unsafe-inline' chrome://resources;"
   }
-}
\ No newline at end of file
+}