Revert regression in AudioBufferSourceNode.start() with no buffer

Revert regression in AudioBufferSourceNode.start() with no buffer

Fix regression introduced in
https://codereview.chromium.org/54173005. That CL prevented the user
from calling start() before setting a buffer source for the
AudioBufferSourceNode.  Previously, this was allowed and when the
buffer was set it would get played. This CL brings back that behavior.

The WebAudio spec is silent on this issue, but this was raised on the
W3C audio list
(http://lists.w3.org/Archives/Public/public-audio/2014JanMar/0059.html)
and there was no apparent opposition to keeping the old behavior.

This also allows http://chromium.googlecode.com/svn/trunk/samples/audio/wavetable-synth.html to work again since it calls start with null buffer which is set later.

BUG=334237
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=168161

[Raymond Toy (Google), 2014-02-13 17:35:19]

PTAL

[Raymond Toy (Google), 2014-02-28 00:04:02]

Ping

[Ken Russell (switch to Gerrit), 2014-02-28 00:33:29]

lgtm

[Raymond Toy (Google), 2014-02-28 00:48:38]

On 2014/02/28 00:33:29, Ken Russell wrote:
> lgtm

Thanks!

[Raymond Toy (Google), 2014-02-28 00:48:48]

The CQ bit was checked by rtoy@google.com

[commit-bot: I haz the power, 2014-02-28 00:49:05]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/rtoy@google.com/161553002/1

[commit-bot: I haz the power, 2014-02-28 01:12:51]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/rtoy@google.com/161553002/1

[Sergey Berezin, 2014-02-28 18:47:27]

The CQ bit was unchecked by sergeyberezin@chromium.org

[Sergey Berezin, 2014-02-28 18:47:56]

The CQ bit was checked by sergeyberezin@chromium.org

[commit-bot: I haz the power, 2014-02-28 18:48:04]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/rtoy@google.com/161553002/1

[commit-bot: I haz the power, 2014-02-28 19:57:31]

Change committed as 168161