Revert of Don't ensure, in single-process mode, that WebUI render views are the only ones in the process, as … (patchset #5 id:80001 of https://codereview.chromium.org/298133002/)

Reason for revert:
This patch broke the memory.fyi bots, as they run tests in single-process mode.

http://build.chromium.org/p/chromium.memory.fyi/builders/Linux%20Tests%20%28valgrind%29%281%29/builds/36766

Original issue's description:
> Don't ensure, in single-process mode, that WebUI render views are the only ones in the process, as it makes no sense
>  - we have single process only and no process-separation is expected.
>
> This allows testing navigation between WebUI and standard pages
> in single-process mode.
>
> BUG=
>
> Committed: https://crrev.com/bf50b9cc28f7a7749183a6c241c4836d5a66c54c
> Cr-Commit-Position: refs/heads/master@{#297683}

TBR=kolczyk@opera.com
NOTREECHECKS=true
NOTRY=true
BUG=

Review URL: https://codereview.chromium.org/618853004

Cr-Commit-Position: refs/heads/master@{#297705}
2 files changed