NaCl: Merge three global PP_Instance mappings into one

NaCl: Merge three global PP_Instance mappings into one

components/nacl/renderer/ had three mappings from PP_Instance IDs:
 * mapping to NexeLoadManager
 * mapping to JsonManifest
 * mapping to InstanceInfo

Merging these into one will make it easier to add more per-PP_Instance
state in the future.

This also makes the lifetime of the objects mapped from PP_Instances
clearer.  This should fix a leak of InstanceInfo if untrusted code
never calls the StartPpapiProxy IPC (though the IPC::ChannelHandle in
it will still leak since this isn't owned).

BUG=428030
TEST=NaCl tests in browser_tests

Committed: https://crrev.com/9f45f6309ae6cbeaf1b08844f32c4579df3acf18
Cr-Commit-Position: refs/heads/master@{#312540}

[Mark Seaborn, 2015-01-21 22:12:44]

mseaborn@chromium.org changed reviewers:
+ teravest@chromium.org

[Mark Seaborn, 2015-01-21 22:13:46]

You might want to check that this has NULL checks in the places where they are
needed.  (As we were discussing in IM, it's not clear where exactly they're
needed.)

[teravest, 2015-01-21 23:47:42]

lgtm

I agree this is clearer, thanks! The NULL checks look right to me.

[Mark Seaborn, 2015-01-22 00:58:46]

The CQ bit was checked by mseaborn@chromium.org

[commit-bot: I haz the power, 2015-01-22 01:00:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/856583003/80001

[commit-bot: I haz the power, 2015-01-22 02:42:12]

Committed patchset #5 (id:80001)

[commit-bot: I haz the power, 2015-01-22 02:43:07]

Patchset 5 (id:??) landed as
https://crrev.com/9f45f6309ae6cbeaf1b08844f32c4579df3acf18
Cr-Commit-Position: refs/heads/master@{#312540}