Fix iframe cases in per-origin noScript

[yrliou]

Description

Per-origin noScript is broken for scripts in iframes, probably after site-per-process became default.

Steps to Reproduce

1. Visit brianbondy.com in a new tab
2. Block scripts from shields
3. Toggle switch to allow scripts from brianbondy.com and click apply.
4. After page is auto reloaded, toggle switch to allow scripts from youtube.com and click apply
5. After page is auto reloaded, check whether the youtube iframe in this page is working normally.

Actual result:

youtube iframe is not working and scripts from youtube.com are still blocked.

Expected result:

youtube iframe is working fine and scripts from youtube.com are not blocked.

Reproduces how often:

Easy

Brave version (chrome://version info)

0.55.6

[LaurenWags]

Verified passed with

Brave	0.55.10 Chromium: 70.0.3538.22 (Official Build) beta(64-bit)
Revision	ac9418ba9c3bd7f6baaffa0b055dfe147e0f8364-refs/branch-heads/3538@{#468}
OS	Mac OS X

Verification passed on

Brave	0.55.11 Chromium: 70.0.3538.35 (Official Build) beta (64-bit)
Revision	28dcb499844fa40c28d5f62e337876cb936f79f5-refs/branch-heads/3538@{#678}
OS	Windows 7

Verification Passed on

Brave	0.55.11 Chromium: 70.0.3538.35 (Official Build) beta (64-bit)
Revision	28dcb499844fa40c28d5f62e337876cb936f79f5-refs/branch-heads/3538@{#678}
OS	Linux