Check that buffer exists before trying to get its duration.

Check that buffer exists before trying to get its duration.

Add a simple test for this as well.

BUG=

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=161005

[Raymond Toy (Google), 2013-10-30 20:48:23]

PTAL

[Ken Russell (switch to Gerrit), 2013-10-30 23:07:27]

lgtm

[Ken Russell (switch to Gerrit), 2013-10-30 23:07:50]

P.S. No bug ID?

[Raymond Toy (Google), 2013-10-30 23:14:00]

On 2013/10/30 23:07:50, Ken Russell wrote:
> P.S. No bug ID?

Should I file one? I just found this problem by accident while working on a
different issue and thought I should fix this right away.

[Ken Russell (switch to Gerrit), 2013-10-30 23:17:02]

On 2013/10/30 23:14:00, rtoy wrote:
> On 2013/10/30 23:07:50, Ken Russell wrote:
> > P.S. No bug ID?
> 
> Should I file one? I just found this problem by accident while working on a
> different issue and thought I should fix this right away.

It's not that important. I thought it might have been an oversight.

[Raymond Toy (Google), 2013-10-30 23:18:05]

On 2013/10/30 23:17:02, Ken Russell wrote:
> On 2013/10/30 23:14:00, rtoy wrote:
> > On 2013/10/30 23:07:50, Ken Russell wrote:
> > > P.S. No bug ID?
> > 
> > Should I file one? I just found this problem by accident while working on a
> > different issue and thought I should fix this right away.
> 
> It's not that important. I thought it might have been an oversight.

Ok. Thanks for the review!

[commit-bot: I haz the power, 2013-10-30 23:18:29]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/rtoy@google.com/50363005/30001

[commit-bot: I haz the power, 2013-10-31 02:13:33]

Change committed as 161005