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

Revert of Revert of Remove the last piece of deprecated synchronous IO code. (patchset #1 of https://codereview.chromium.org/509893002/)

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

Original issue's description:
> 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
> BUG=337096
> 
> Committed: https://chromium.googlesource.com/chromium/src/+/3e8c19c89c16fe8a7c2dfe0cae2990cd4a004339

TBR=dalecurtis@chromium.org,ajm@chromium.org,rkc@chromium.org,avi@chromium.org,palmer@chromium.org,tnagel@chromium.org
NOTREECHECKS=true
BUG=337096
Committed: https://crrev.com/421cc21a251e4828fe3065884a9fdf1a47b49d07
Cr-Commit-Position: refs/heads/master@{#292463}

[no longer working on chromium, 2014-08-28 18:14:07]

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

[no longer working on chromium, 2014-08-28 18:14:38]

The CQ bit was unchecked by xians@chromium.org

[no longer working on chromium, 2014-08-28 18:15:01]

The CQ bit was checked by xians@chromium.org

[commit-bot: I haz the power, 2014-08-28 18:15:20]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/xians@chromium.org/518433002/1

[commit-bot: I haz the power, 2014-08-28 21:10:39]

Committed patchset #1 (id:1) as 6410af57e1fbc5b3d9c91b2ad05328578e331301

[commit-bot: I haz the power, 2014-09-10 03:02:16]

Patchset 1 (id:??) landed as
https://crrev.com/421cc21a251e4828fe3065884a9fdf1a47b49d07
Cr-Commit-Position: refs/heads/master@{#292463}