[Extensions] Expand capabilities to about:blank iframes within a page

[Extensions] Expand capabilities to about:blank iframes within a page

Expand the content capabilies to grant the capabilities to about:blank
iframes within a page that matches the content capabilities entry for
an extension. This is consistent with most web permissions, where
about:blank frames take the permissions from the "parent".

In theory, we could also create a match_about_blank entry in the
manifest for this, but I'm not sure how many use cases there are for
*not* granting permissions to child frames like this.

BUG=599900
Review-Url: https://codereview.chromium.org/1985323002
Cr-Commit-Position: refs/heads/master@{#395744}
(cherry picked from commit d0f2bad624766048836545ab34e13cd7a46c92e8)

Committed: https://chromium.googlesource.com/chromium/src/+/c696c1e934654abe2b5362396c6c996c3a9dffeb

[Devlin, 2016-05-31 20:52:05]

Description was changed from

==========
[Extensions] Expand capabilities to about:blank iframes within a page

Expand the content capabilies to grant the capabilities to about:blank
iframes within a page that matches the content capabilities entry for
an extension. This is consistent with most web permissions, where
about:blank frames take the permissions from the "parent".

In theory, we could also create a match_about_blank entry in the
manifest for this, but I'm not sure how many use cases there are for
*not* granting permissions to child frames like this.

BUG=599900

Review-Url: https://codereview.chromium.org/1985323002
Cr-Commit-Position: refs/heads/master@{#395744}
(cherry picked from commit d0f2bad624766048836545ab34e13cd7a46c92e8)
==========

to

==========
[Extensions] Expand capabilities to about:blank iframes within a page

Expand the content capabilies to grant the capabilities to about:blank
iframes within a page that matches the content capabilities entry for
an extension. This is consistent with most web permissions, where
about:blank frames take the permissions from the "parent".

In theory, we could also create a match_about_blank entry in the
manifest for this, but I'm not sure how many use cases there are for
*not* granting permissions to child frames like this.

BUG=599900

Review-Url: https://codereview.chromium.org/1985323002
Cr-Commit-Position: refs/heads/master@{#395744}
(cherry picked from commit d0f2bad624766048836545ab34e13cd7a46c92e8)

Committed:
https://chromium.googlesource.com/chromium/src/+/c696c1e934654abe2b5362396c6c...
==========

[Devlin, 2016-05-31 20:52:07]

Committed patchset #1 (id:1) manually as
c696c1e934654abe2b5362396c6c996c3a9dffeb.