Prevent extension sideloading from Windows registry

Track Windows registry-sideloaded extensions.

This adds a creation flag for extensions which tracks if they
were installed from a potentially untrusted source.

The flag is currently set for extensions which are installed
via the Windows registry from a CRX on the local filesystem.

No enforcement action is being taken yet and no additional metrics are being collected.

BUG=325469
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=290122

[Ken Rockot(use gerrit already), 2014-08-15 17:48:18]

Here's the patch to prevent registry side-loading (of extensions only) from
local filesystem paths. Not sure we actually want to pull the trigger on this
yet, but this will do the trick if needed. I added a questionable string for the
related installation error, but it's not clear how this would ever be exposed in
the UI.

CC erikkay FYI

[asargent_no_longer_on_chrome, 2014-08-15 20:01:16]

If we're going to allow apps, we should probably allow themes also. 

Otherwise code changes lgtm. 

Make sure to get at least the strings part of the change in today.

[Ken Rockot(use gerrit already), 2014-08-15 23:25:10]

On 2014/08/15 20:01:16, Antony Sargent wrote:
> If we're going to allow apps, we should probably allow themes also. 
> 
> Otherwise code changes lgtm. 
> 
> Make sure to get at least the strings part of the change in today.

After some investigation, we decided it's probably too risky to do include any
real enforcement in this CL. For now this just hooks up a new "maybe we don't
trust you" flag with no further action.

[Ken Rockot(use gerrit already), 2014-08-15 23:25:23]

The CQ bit was checked by rockot@chromium.org

[commit-bot: I haz the power, 2014-08-15 23:28:35]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/rockot@chromium.org/479513004/60001

[Ken Rockot(use gerrit already), 2014-08-16 00:53:37]

The CQ bit was checked by rockot@chromium.org

[commit-bot: I haz the power, 2014-08-16 00:55:39]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/rockot@chromium.org/479513004/80001

[commit-bot: I haz the power, 2014-08-16 07:58:11]

Committed patchset #3 (80001) as 290122

[Evan Stade, 2014-12-20 01:27:59]

estade@chromium.org changed reviewers:
+ estade@chromium.org

[Evan Stade, 2014-12-20 01:27:59]

https://codereview.chromium.org/479513004/diff/80001/chrome/app/generated_res...
File chrome/app/generated_resources.grd (right):

https://codereview.chromium.org/479513004/diff/80001/chrome/app/generated_res...
chrome/app/generated_resources.grd:4560: +        Cannot install untrusted
extension with ID "<ph
name="IMPORT_ID">$1<ex>aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa</ex></ph>."
It seems this is not used anywhere. Can it be removed?