Revert of Remove the last piece of deprecated synchronous IO code.

Revert of Remove the last piece of deprecated synchronous IO code. (patchset #5 of https://codereview.chromium.org/460373002/)

Reason for revert:
Build failure on Google Chrome ChromeOS:

http://build.chromium.org/p/chromium.chrome/buildstatus?builder=Google%20Chrome%20ChromeOS&number=71164

Original issue's description:
> Remove the last piece of deprecated synchronous IO code.
> 
> BUG=337096
> TEST=bots
> 
> Committed: https://chromium.googlesource.com/chromium/src/+/c4a64ffdd0d511c66d774341fa0a318af7911193

TBR=dalecurtis@chromium.org,ajm@chromium.org,rkc@chromium.org,avi@chromium.org,palmer@chromium.org,xians@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=337096
Committed: https://crrev.com/688335507909215843b37f201787da80d8b68266
Cr-Commit-Position: refs/heads/master@{#292133}

[Thiemo Nagel, 2014-08-27 11:00:35]

Created Revert of Remove the last piece of deprecated synchronous IO code.

[commit-bot: I haz the power, 2014-08-27 11:01:06]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/tnagel@chromium.org/509893002/1

[commit-bot: I haz the power, 2014-08-27 11:02:15]

Committed patchset #1 (1) as 3e8c19c89c16fe8a7c2dfe0cae2990cd4a004339

[rkc, 2014-08-27 11:36:21]

I'll fix this today. The ledger repo no longer needs to build since all the code
is open sourced, I just forgot to remove it.

[no longer working on chromium, 2014-08-28 18:14:06]

A revert of this CL (patchset #1) has been created in
https://codereview.chromium.org/518433002/ by xians@chromium.org.

The reason for reverting is: https://codereview.chromium.org/510893003/ fixed
the ledger bot, so I am going to revert this revert CL..

[commit-bot: I haz the power, 2014-09-10 02:51:04]

Patchset 1 (id:??) landed as
https://crrev.com/688335507909215843b37f201787da80d8b68266
Cr-Commit-Position: refs/heads/master@{#292133}