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Modify permissions and checks in GuestView, WebUI, and
extensions to allow <extensionoptions> to be used within WebUI.
In the GuestView infrastructure, allow guest views in WebUI to
be created without extension ids. In extensions, allow extension
options-related APIs to be used in WebUI contexts. In WebUI,
relax the CSP to allow internal browser plugins.  


BUG=386842

Review URL: https://codereview.chromium.org/453613002

Cr-Commit-Position: refs/heads/master@{#289233}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@289233 0039d316-1c4b-4281-b951-d872f2087c98