Revert 133359 - Relanding r133313.

Revert 133359 - Relanding r133313.

I've reordered the resource request URLRequest cancellations so now I can reland r133313 and not have it assert on renderer resource requests.

==========

Revert 133313 - I need to move the assertion to a better place.

Assert when URLRequests leak for the main URLRequestContexts.

I've already enabled the assertions for all the non-main URLRequestContexts:
  * safe browsing
  * system
  * media
  * extensions

I've squashed those leaks, so now it's time to work on the main URLRequestContext for the profile. I know there are defintely existing l

BUG=90971
TEST=none

==========

TBR=eroman
BUG=90971
TEST=none


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=133842

[commit-bot: I haz the power, 2012-04-25 00:36:26]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/willchan@chromium.org/10219010/1

[commit-bot: I haz the power, 2012-04-25 02:15:01]

Change committed as 133842