Revert of Revert of Merge VideoDecodeAcceleratorImpl with VideoDecodeAccelerator

Revert of Revert of Merge VideoDecodeAcceleratorImpl with VideoDecodeAccelerator (https://codereview.chromium.org/319323002/)

Reason for revert:
Relanding since the failure appears to be unrelated.

Original issue's description:
> Revert of Merge VideoDecodeAcceleratorImpl with VideoDecodeAccelerator (https://codereview.chromium.org/317083003/)
> 
> Reason for revert:
> Speculative revert to fix content_unittest failures in http://build.chromium.org/p/chromium.linux/builders/Android%20Tests%20%28dbg%29/builds/20807
> 
> Original issue's description:
> > Merge VideoDecodeAcceleratorImpl with VideoDecodeAccelerator
> > 
> > This moves the single method CanDecodeOnIOThread on
> > VideoDecodeAcceleratorImpl to VideoDecodeAccelerator. The
> > implementations that were subclasses of VideoDecodeAcceleratorImpl now
> > get an override for CanDecodeOnIOThread that returns false.
> > 
> > TEST=linux desktop build
> > BUG=380884
> > 
> > Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=275621
> 
> TBR=scherkus@chromium.org,fischman@chromium.org,spang@chromium.org
> NOTREECHECKS=true
> NOTRY=true
> BUG=380884
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=275636

TBR=scherkus@chromium.org,fischman@chromium.org,spang@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=380884
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=275669

[dcheng, 2014-06-07 08:20:51]

Created Revert of Revert of Merge VideoDecodeAcceleratorImpl with
VideoDecodeAccelerator

[commit-bot: I haz the power, 2014-06-07 08:21:39]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/dcheng@chromium.org/318243002/1

[commit-bot: I haz the power, 2014-06-07 09:13:54]

Change committed as 275669