Revert of content: Use NumberOfProcessors() / 2 raster threads.

Revert of content: Use NumberOfProcessors() / 2 raster threads. (patchset #2 id:20001 of https://codereview.chromium.org/1143473002/)

Reason for revert:
Incorrect logic for determining if async uploads is used

Original issue's description:
> content: Use NumberOfProcessors() / 2 raster threads.
>
> 4 raster threads improve performance on 8 core machines.
> 8 core machines might not be a priority but it seems
> like an unnecessary limitation to have.
>
> BUG=
>
> Committed: https://crrev.com/4a0177a1dba8197f61021ff3b4f9426e45faaa62
> Cr-Commit-Position: refs/heads/master@{#330427}

TBR=danakj@chromium.org,enne@chromium.org,piman@chromium.org,vmpstr@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=

Committed: https://crrev.com/55eaae181aba5febcad9d54aff66822a691a94b7
Cr-Commit-Position: refs/heads/master@{#330520}

[reveman, 2015-05-19 16:41:54]

Created Revert of content: Use NumberOfProcessors() / 2 raster threads.

[commit-bot: I haz the power, 2015-05-19 16:42:23]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1136633006/1

[commit-bot: I haz the power, 2015-05-19 16:44:00]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-19 16:44:48]

Patchset 1 (id:??) landed as
https://crrev.com/55eaae181aba5febcad9d54aff66822a691a94b7
Cr-Commit-Position: refs/heads/master@{#330520}