media: Pass SetCdmReadyCB in {Audio|Video}Decoder::Initialize().

media: Pass SetCdmReadyCB in {Audio|Video}Decoder::Initialize().

(This reverts commit 0c1df0a37a815953d1af3d4eaf145af969210d5d with fix.)

This enables all audio/video decoders the ability to get access to the CDM
associated with the media element. This is useful for certain decoders to handle
encrypted streams.

For Decrypting{Audio|Video}Decoder and DecryptingDemuxerStream, the SetCdmReadyCB
is simply moved from constructor to Initialize() call. In the future this could
also help move Decrypting{Audio|Video}Decoder creation out of DecoderSelector so
that it is treated the same as all other decoders.

TBR=bbudge@chromium.org,jrummell@chromium.org,dalecurtis@chromium.org
BUG=545099
Committed: https://crrev.com/680a312fa2dfe2fccce0ecc1d00193fa6d4be29b
Cr-Commit-Position: refs/heads/master@{#359754}

[xhwang, 2015-11-14 06:28:33]

The CQ bit was checked by xhwang@chromium.org

[commit-bot: I haz the power, 2015-11-14 06:29:49]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1447533006/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1447533006/1

[commit-bot: I haz the power, 2015-11-14 08:19:52]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-11-14 08:19:54]

Try jobs failed on following builders:
  mac_chromium_rel_ng on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_rel_...)

[xhwang, 2015-11-14 22:12:46]

The CQ bit was checked by xhwang@chromium.org

[commit-bot: I haz the power, 2015-11-14 22:13:26]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1447533006/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1447533006/1

[commit-bot: I haz the power, 2015-11-15 02:42:10]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-15 02:43:40]

Patchset 1 (id:??) landed as
https://crrev.com/680a312fa2dfe2fccce0ecc1d00193fa6d4be29b
Cr-Commit-Position: refs/heads/master@{#359754}