Revert changes from r152523 and split bitstream converter creation and enabling.

Revert changes from r152523 and split bitstream converter creation and enabling.
Bitstream converter now gets created when we know the FFmpeg structs are
valid. Enabling the converter no longer needs access to these structs so the
crash is avoided.




BUG=144432
TEST=Manual testing with GPU video decoder init failing and falling back to software decode.

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=153204

[acolwell GONE FROM CHROMIUM, 2012-08-24 01:11:40]

This may look familiar. ;) I've verified this works properly when GPU video
initialization fails. 

I plan to provide a follow-up CL that will modify PipelineIntegrationTest to
test for the GpuVideoDecoder failed init scenario.

[Ami GONE FROM CHROMIUM, 2012-08-24 02:52:30]

LGTM
we should do all our coding & reviewing this way!

[commit-bot: I haz the power, 2012-08-24 06:06:24]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/acolwell@chromium.org/10879057/1

[commit-bot: I haz the power, 2012-08-24 09:35:56]

Try job failure for 10879057-1 (retry) on linux_chromeos for step
"browser_tests".
It's a second try, previously, step "browser_tests" failed.
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=linux_chro...