Revert of Remove AudioBuffer::set_duration(), instead base on frames.

Revert of Remove AudioBuffer::set_duration(), instead base on frames. (https://codereview.chromium.org/261533002/)

Reason for revert:
This seems to have broken the chromium.webkit WebKit Win x64 Builder bot.

Log: http://build.chromium.org/p/chromium.webkit/builders/WebKit%20Win%20x64%20Builder/builds/6453

Snippet from log:
c:\b\build\slave\webkit-win-latest-rel-x64\build\src\media\base\audio_buffer.cc(16) : error C2220: warning treated as error - no 'object' file generated
c:\b\build\slave\webkit-win-latest-rel-x64\build\src\media\base\audio_buffer.cc(16) : warning C4723: potential divide by 0

Original issue's description:
> Remove AudioBuffer::set_duration(), instead base on frames.
> 
> wolenetz@ asked on https://codereview.chromium.org/251893002/ why
> we allow set_duration() to be called.  It used to be required since
> AudioBuffers had no concept of sample rate.  However, we now attach
> a sample rate to every AudioBuffer which allows us to enforce a
> valid duration for every buffer.
> 
> This CL also aligns MakeAudioBuffer() to do the same thing with
> planar and interleaved data for the sake of easier testing.
> 
> BUG=none
> TEST=media_unittests
> NOTRY=true
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=267779

TBR=jrummell@chromium.org,dmichael@chromium.org,dalecurtis@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=none

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=267788

[falken, 2014-05-02 10:50:30]

Created Revert of Remove AudioBuffer::set_duration(), instead base on frames.

[falken, 2014-05-02 10:51:07]

The CQ bit was checked by falken@chromium.org

[commit-bot: I haz the power, 2014-05-02 10:51:26]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/falken@chromium.org/265943002/1

[commit-bot: I haz the power, 2014-05-02 10:52:26]

Change committed as 267788