Workaround for reading bad PageState from session history.

Workaround for reading bad PageState from session history.

If no history item is found for a subframe and the fallback URL
is about:blank, the browser doesn't need to tell the renderer to
load it again.

BUG=638088
TEST=Load chrome://help, then chrome://restart.
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_site_isolation

[Charlie Reis, 2016-08-20 03:57:27]

Description was changed from

==========
Workaround for reading bad PageState from session history.

If no history item is found for a subframe and the fallback URL
is about:blank, the browser doesn't need to tell the renderer to
load it again.

BUG=638088
TEST=Load chrome://help, then chrome://restart.
==========

to

==========
Workaround for reading bad PageState from session history.

If no history item is found for a subframe and the fallback URL
is about:blank, the browser doesn't need to tell the renderer to
load it again.

BUG=638088
TEST=Load chrome://help, then chrome://restart.
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_site_isolation
==========

[Charlie Reis, 2016-08-20 03:57:33]

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

[commit-bot: I haz the power, 2016-08-20 03:57:47]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-08-20 04:04:09]

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

[commit-bot: I haz the power, 2016-08-20 04:04:10]

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