Revert of Merge VideoDecodeAcceleratorImpl with VideoDecodeAccelerator

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

[dcheng, 2014-06-07 07:16:08]

Created Revert of Merge VideoDecodeAcceleratorImpl with VideoDecodeAccelerator

[commit-bot: I haz the power, 2014-06-07 07:18:19]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/dcheng@chromium.org/319323002/1

[commit-bot: I haz the power, 2014-06-07 07:19:59]

Change committed as 275636

[dcheng, 2014-06-07 08:20:50]

A revert of this CL has been created in
https://codereview.chromium.org/318243002/ by dcheng@chromium.org.

The reason for reverting is: Relanding since the failure appears to be
unrelated..