Cast: Fix threading issues in VideoEncoderImpl

Cast: Fix threading issues in VideoEncoderImpl

VideoEncoderImpl can be used after delete. We assumed that main thread
out-live video encoder thread. This is not true for some use cases. For
example in the renderer when video encoder thread is shared by multiple
instances of CastSEnder. To fix this we need to separate Vp8Encoder and
VideoEncoderImpl.

VideoEncoderImpl will live on the main thread only. And Vp8Encoder will
live on the video encoder thread only.

Tested this change with vagrind and cast_unittests reports no error.

TBR=mikhal@chromium.org
BUG=336887
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=246974

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=247092

[Alpha Left Google, 2014-01-24 01:45:34]

This had been LGTMed in https://codereview.chromium.org/145443005/.

I just split the change in VideoEncoderImpl into this change. Landing as TBR.

[commit-bot: I haz the power, 2014-01-24 01:46:43]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/hclam@chromium.org/138953009/80001

[commit-bot: I haz the power, 2014-01-24 19:30:48]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/hclam@chromium.org/138953009/200001

[commit-bot: I haz the power, 2014-01-24 21:35:41]

Change committed as 246974

[Alpha Left Google, 2014-01-24 22:26:58]

A revert of this CL has been created in
https://codereview.chromium.org/132283006/ by hclam@chromium.org.

The reason for reverting is: build break..

[Alpha Left Google, 2014-01-24 22:39:20]

I know what happened. There's one change that got dropped in the cl. that's why
it's causing crashes.

[Alpha Left Google, 2014-01-24 22:40:36]

On 2014/01/24 22:39:20, Alpha wrote:
> I know what happened. There's one change that got dropped in the cl. that's
why
> it's causing crashes.

I had a bad merge that caused the change in encode_decode_test to be dropped.
Landing this again.

[commit-bot: I haz the power, 2014-01-24 22:41:51]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/hclam@chromium.org/138953009/560001

[commit-bot: I haz the power, 2014-01-25 00:28:48]

Retried try job too often on win_rel for step(s) telemetry_perf_unittests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win_rel&nu...

[commit-bot: I haz the power, 2014-01-25 01:20:24]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/hclam@chromium.org/138953009/560001

[commit-bot: I haz the power, 2014-01-25 07:42:43]

Change committed as 247092