Revert of If SRTP sessions exist, don't create new ones when applying answer.

Revert of If SRTP sessions exist, don't create new ones when applying answer. (patchset #1 id:1 of https://codereview.webrtc.org/3019443002/ )

Reason for revert:
Looks like it causes a crash on Chrome Android browser tests: https://build.chromium.org/p/chromium.webrtc.fyi/waterfall?builder=Android%20Tests%20(dbg)%20(K%20Nexus5)

Original issue's description:
> If SRTP sessions exist, don't create new ones when applying answer.
> 
> Instead, call the "Update" methods of SrtpSession, which will just call
> srtp_update, instead of wiping out the session state completely.
> 
> This was causing decryption to stop working when subsequent
> offers/answers are applied. We don't know enough about SRTP to
> understand the root cause, and I wasn't able to write an integration
> test that reproduces the issue... But at least this fixes the bug that
> can be reproduced reliably using Hangouts.
> 
> BUG=webrtc:8251
> 
> Review-Url: https://codereview.webrtc.org/3019443002
> Cr-Commit-Position: refs/heads/master@{#19874}
> Committed: https://webrtc.googlesource.com/src/+/5ada7acf603e90e71990e9d4ff8f49389f24958c

TBR=zhihuang@webrtc.org,deadbeef@webrtc.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=webrtc:8251

[phoglund, 2017-09-18 09:26:04]

The CQ bit was checked by phoglund@webrtc.org

[phoglund, 2017-09-18 09:26:05]

Created Revert of If SRTP sessions exist, don't create new ones when applying
answer.

[commit-bot: I haz the power, 2017-09-18 09:26:15]

CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.webrtc.org/...

[commit-bot: I haz the power, 2017-09-18 10:36:48]

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

[commit-bot: I haz the power, 2017-09-18 10:36:49]

Failed to apply the patch.
On branch working_branch
Your branch is up-to-date with 'origin/refs/heads/master'.
nothing to commit, working tree clean

[phoglund, 2017-09-18 10:46:39]

Description was changed from

==========
Revert of If SRTP sessions exist, don't create new ones when applying answer.
(patchset #1 id:1 of https://codereview.webrtc.org/3019443002/ )

Reason for revert:
Looks like it causes a crash on Chrome Android browser tests:
https://build.chromium.org/p/chromium.webrtc.fyi/waterfall?builder=Android%20...

Original issue's description:
> If SRTP sessions exist, don't create new ones when applying answer.
> 
> Instead, call the "Update" methods of SrtpSession, which will just call
> srtp_update, instead of wiping out the session state completely.
> 
> This was causing decryption to stop working when subsequent
> offers/answers are applied. We don't know enough about SRTP to
> understand the root cause, and I wasn't able to write an integration
> test that reproduces the issue... But at least this fixes the bug that
> can be reproduced reliably using Hangouts.
> 
> BUG=webrtc:8251
> 
> Review-Url: https://codereview.webrtc.org/3019443002
> Cr-Commit-Position: refs/heads/master@{#19874}
> Committed:
https://webrtc.googlesource.com/src/+/5ada7acf603e90e71990e9d4ff8f49389f24958c

TBR=zhihuang@webrtc.org,deadbeef@webrtc.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=webrtc:8251
==========

to

==========
Revert of If SRTP sessions exist, don't create new ones when applying answer.
(patchset #1 id:1 of https://codereview.webrtc.org/3019443002/ )

Reason for revert:
Looks like it causes a crash on Chrome Android browser tests:
https://build.chromium.org/p/chromium.webrtc.fyi/waterfall?builder=Android%20...

Original issue's description:
> If SRTP sessions exist, don't create new ones when applying answer.
> 
> Instead, call the "Update" methods of SrtpSession, which will just call
> srtp_update, instead of wiping out the session state completely.
> 
> This was causing decryption to stop working when subsequent
> offers/answers are applied. We don't know enough about SRTP to
> understand the root cause, and I wasn't able to write an integration
> test that reproduces the issue... But at least this fixes the bug that
> can be reproduced reliably using Hangouts.
> 
> BUG=webrtc:8251
> 
> Review-Url: https://codereview.webrtc.org/3019443002
> Cr-Commit-Position: refs/heads/master@{#19874}
> Committed:
https://webrtc.googlesource.com/src/+/5ada7acf603e90e71990e9d4ff8f49389f24958c

TBR=zhihuang@webrtc.org,deadbeef@webrtc.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=webrtc:8251
==========

[phoglund, 2017-09-18 10:46:57]

Henrika just beat me to it, closing this one.