Fix blob URL blocking for apps that use <webview>.

Fix blob URL blocking for apps that use <webview>.

It should be possible for an app to embed a <webview> and navigate it
to a blob URL that the app creates.  In a previous security fix
(r419019), this navigation was unintentionally blocked, due to
<webview> being considered a main frame as well as being in an
untrusted web process which is requesting a blob URL in a
chrome-extension:// scheme.

BUG=652077, 645028
Review-Url: https://codereview.chromium.org/2387323002
Cr-Commit-Position: refs/heads/master@{#422954}
(cherry picked from commit cd20702d3b3dd5224beaa7fd7b876313b33b6b70)

Committed: https://chromium.googlesource.com/chromium/src/+/01928f6ddee40f6e2e5041013c2773e515176955

[alexmos, 2016-10-05 21:40:15]

Description was changed from

==========
Fix blob URL blocking for apps that use <webview>.

It should be possible for an app to embed a <webview> and navigate it
to a blob URL that the app creates.  In a previous security fix
(r419019), this navigation was unintentionally blocked, due to
<webview> being considered a main frame as well as being in an
untrusted web process which is requesting a blob URL in a
chrome-extension:// scheme.

BUG=652077,645028

Review-Url: https://codereview.chromium.org/2387323002
Cr-Commit-Position: refs/heads/master@{#422954}
(cherry picked from commit cd20702d3b3dd5224beaa7fd7b876313b33b6b70)
==========

to

==========
Fix blob URL blocking for apps that use <webview>.

It should be possible for an app to embed a <webview> and navigate it
to a blob URL that the app creates.  In a previous security fix
(r419019), this navigation was unintentionally blocked, due to
<webview> being considered a main frame as well as being in an
untrusted web process which is requesting a blob URL in a
chrome-extension:// scheme.

BUG=652077,645028

Review-Url: https://codereview.chromium.org/2387323002
Cr-Commit-Position: refs/heads/master@{#422954}
(cherry picked from commit cd20702d3b3dd5224beaa7fd7b876313b33b6b70)

Committed:
https://chromium.googlesource.com/chromium/src/+/01928f6ddee40f6e2e5041013c27...
==========

[alexmos, 2016-10-05 21:40:17]

Committed patchset #1 (id:1) manually as
01928f6ddee40f6e2e5041013c2773e515176955.