Add DCHECK to detect when a RPH is reused with a different context.

Add DCHECK to detect when a RPH is reused with a different context.

When running in single-process mode (as happens in tests) we always
attempt to reuse an existing render process host. If a previous test
does not clean up properly then this render process host will be
associated with a (now invalid) BrowserContext.

This DCHECK assists in discovering test cases where this happens without
running the tests under a memory error detector such as MSan.

BUG=608064
Committed: https://crrev.com/7b5641ee5ec1f5517924b020ad6265d4ffcaeabd
Cr-Commit-Position: refs/heads/master@{#391865}

[Reilly Grant (use Gerrit), 2016-05-03 21:50:05]

reillyg@chromium.org changed reviewers:
+ jam@chromium.org

[Reilly Grant (use Gerrit), 2016-05-03 21:50:06]

jam@, this is the DCHECK we discussed adding.

[jam, 2016-05-05 15:24:59]

lgtm

[Reilly Grant (use Gerrit), 2016-05-05 17:43:09]

The CQ bit was checked by reillyg@chromium.org

[commit-bot: I haz the power, 2016-05-05 17:43:32]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1943403003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1943403003/1

[commit-bot: I haz the power, 2016-05-05 19:18:01]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-05-05 19:19:23]

Description was changed from

==========
Add DCHECK to detect when a RPH is reused with a different context.

When running in single-process mode (as happens in tests) we always
attempt to reuse an existing render process host. If a previous test
does not clean up properly then this render process host will be
associated with a (now invalid) BrowserContext.

This DCHECK assists in discovering test cases where this happens without
running the tests under a memory error detector such as MSan.

BUG=608064
==========

to

==========
Add DCHECK to detect when a RPH is reused with a different context.

When running in single-process mode (as happens in tests) we always
attempt to reuse an existing render process host. If a previous test
does not clean up properly then this render process host will be
associated with a (now invalid) BrowserContext.

This DCHECK assists in discovering test cases where this happens without
running the tests under a memory error detector such as MSan.

BUG=608064

Committed: https://crrev.com/7b5641ee5ec1f5517924b020ad6265d4ffcaeabd
Cr-Commit-Position: refs/heads/master@{#391865}
==========

[commit-bot: I haz the power, 2016-05-05 19:19:24]

Patchset 1 (id:??) landed as
https://crrev.com/7b5641ee5ec1f5517924b020ad6265d4ffcaeabd
Cr-Commit-Position: refs/heads/master@{#391865}