Revert of Revalidate using the same Resource, attempt #3

Revert of Revalidate using the same Resource, attempt #3 (patchset #2 id:20001 of https://codereview.chromium.org/1398523004/ )

Reason for revert:
Seems to have caused assertion failures on http://build.chromium.org/p/chromium.gpu/builders/Android%20Debug%20%28Nexus%206%29?numbuilds=200 as described on the original CL.

Original issue's description:
> Revalidate using the same Resource, attempt #3
>
> Currently, when we perform a revalidation, we create a new resource and put it in the MemoryCache in place of the resource being revalidated. If the revalidation results in a 304, we silently swap all of the clients of the revalidation to the now-revalidated resource and swap which Resource is in the MemoryCache.
>
> This changes the behavior to use the existing resource to revalidate itself, which simplifies the logic quite a bit. It also gives us the option of removing ResourcePtr (which is used to implement the silent client swap in the 304 case) and make Resources simply RefCounted in a future change.
>
> BUG=
>
> Committed: https://crrev.com/71adea27213b2268bda765abccd5a3bf9517b860
> Cr-Commit-Position: refs/heads/master@{#354615}

TBR=mkwst@chromium.org,japhet@chromium.org
BUG=

Committed: https://crrev.com/de1ba5f46e2227224a245a54f8de2b85231c55ff
Cr-Commit-Position: refs/heads/master@{#354721}

[Ken Russell (switch to Gerrit), 2015-10-18 23:24:50]

Created Revert of Revalidate using the same Resource, attempt #3

[Ken Russell (switch to Gerrit), 2015-10-18 23:25:07]

The CQ bit was checked by kbr@chromium.org

[commit-bot: I haz the power, 2015-10-18 23:25:15]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1410313002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1410313002/1

[commit-bot: I haz the power, 2015-10-19 03:15:28]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-10-19 03:16:17]

Patchset 1 (id:??) landed as
https://crrev.com/de1ba5f46e2227224a245a54f8de2b85231c55ff
Cr-Commit-Position: refs/heads/master@{#354721}