Revert of Removing "using" declarations that import names in the C++ Standard library.

Revert of Removing "using" declarations that import names in the C++ Standard library. (https://codereview.chromium.org/329183002/)

Reason for revert:
This patch is causing failures on the Chromium Linux Tsan v2 bot: http://build.chromium.org/p/chromium.memory.fyi/builders/Linux%20Builder%20(TSan%20v2)

The problem is that std::abs(int) is found in <cstdlib> but we apparently only include <cmath> everywhere. So the compiler only knows about std::abs(float) and variants.

You can probably fix this by including <cstdlib> in the places where you use std::abs.

Original issue's description:
> Removing "using" declarations that import names in the C++ Standard library.
> 
> This is as per the the coding guidelines for blink, which disallows the
> use of "using" declarations of any kind to import names in the standard
> template library.
> 
> BUG=NONE
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=176032

TBR=tkent@chromium.org,ch.dumez@samsung.com,sunil.ratnu@samsung.com
NOTREECHECKS=true
NOTRY=true
BUG=NONE

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=176125

[Stephen Chennney, 2014-06-13 19:17:50]

Created Revert of Removing "using" declarations that import names in the C++
Standard library.

[commit-bot: I haz the power, 2014-06-13 19:19:05]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/schenney@chromium.org/330933002/1

[commit-bot: I haz the power, 2014-06-13 19:19:52]

Change committed as 176125

[Lei Zhang, 2014-06-14 00:28:01]

On 2014/06/13 19:17:50, Stephen Chenney wrote:
> Created Revert of Removing "using" declarations that import names in the C++
> Standard library.

Thanks for the revert, though I did try to fix it...
https://codereview.chromium.org/338603003/

[haraken, 2014-06-14 00:31:51]

On 2014/06/14 00:28:01, Lei Zhang wrote:
> On 2014/06/13 19:17:50, Stephen Chenney wrote:
> > Created Revert of Removing "using" declarations that import names in the C++
> > Standard library.
> 
> Thanks for the revert, though I did try to fix it...
> https://codereview.chromium.org/338603003/

LGTM to the revert. Let's reland it once Lei's fix is in.