Use Symfony Request for toolbar module

Patch attached.

Needs a reroll... and we already have the request object so this patch is even simpler...

curl https://drupal.org/files/1999442_1-remove-GET-variable-toolbar.patch | git a
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   588  100   588    0     0    501      0  0:00:01  0:00:01 --:--:--   934
error: patch failed: core/modules/toolbar/toolbar.module:130
error: core/modules/toolbar/toolbar.module: patch does not apply

I don't know what this code is doing, but modifying the request is the correct action in about 0.00053% of cases. And those are Drupal design flaws we haven't fixed yet. The odds of this being one of them are low. :-) What's going on in this module, and can we change it to not be wrong?

Bumping. I'm especially confused by the use of $_GET['q'], since that's long since been eliminated as a path value.

this is either cruft and can be safely removed, or it hides a bug..$_GET['q'] is definitely not working..i guess some input from a maintainer of toolbar module is needed

Oh good.

Let's try removing it entirely and see what testbot says breaks. :-)

OK then! :-)

This issue was RTBC and passing tests on July 1, the beginning of API freeze.

I've manually tested the toolbar with page caching enabled and everything is still working as expected.

Committed 7617975 and pushed to 8.x. Thanks!