Tightening checks in ChromeContentBrowserClientExtensionsPart::CanCommitURL

Tightening checks in ChromeContentBrowserClientExtensionsPart::CanCommitURL

Since --isolate-extensions has shipped in M58, we should be able to
enforce stricter CanCommitURL checks and disallow extension frames from
committing outside of an extension process.

BUG=TODO/DO NOT SUBMIT

[Łukasz Anforowicz, 2017-05-26 22:59:22]

The CQ bit was checked by lukasza@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-05-26 22:59:54]

Dry run: CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[Łukasz Anforowicz, 2017-05-26 23:00:20]

Description was changed from

==========
Tightening checks in ChromeContentBrowserClientExtensionsPart::CanCommitURL

BUG=TODO/DO NOT SUBMIT
==========

to

==========
Tightening checks in ChromeContentBrowserClientExtensionsPart::CanCommitURL

Since --isolate-extensions has shipped in M58, we should be able to
enforce stricter CanCommitURL checks and disallow extension frames from
committing outside of an extension process.

BUG=TODO/DO NOT SUBMIT
==========

[commit-bot: I haz the power, 2017-05-26 23:42:59]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-05-26 23:43:00]

Dry run: Try jobs failed on following builders:
  linux_chromium_rel_ng on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)