[MERGE TO M52] Don't recreate the speech encoder if we don't have to

[MERGE TO M52] Don't recreate the speech encoder if we don't have to

If the specification for the speech encoder hasn't changed, we should
reuse it instead of recreating it. Otherwise, we lose its state. (This
problem was originally discovered because AudioEncoderOpus instances
would forget that they were supposed to be using DTX.)

BUG=webrtc:6020, chromium:622647
Review-Url: https://codereview.webrtc.org/2089183002
Cr-Commit-Position: refs/heads/master@{#13273}
(cherry picked from commit 3f81fcd2e845505c2873c7ec2edade910213596b)

Committed: https://chromium.googlesource.com/external/webrtc/+/15a5d9f9e3e4e8591c7a598c3818f42987cff522

[hlundin-webrtc, 2016-06-29 08:27:32]

Description was changed from

==========
[MERGE TO M52] Don't recreate the speech encoder if we don't have to

If the specification for the speech encoder hasn't changed, we should
reuse it instead of recreating it. Otherwise, we lose its state. (This
problem was originally discovered because AudioEncoderOpus instances
would forget that they were supposed to be using DTX.)

BUG=webrtc:6020, chromium:622647

Review-Url: https://codereview.webrtc.org/2089183002
Cr-Commit-Position: refs/heads/master@{#13273}
(cherry picked from commit 3f81fcd2e845505c2873c7ec2edade910213596b)
==========

to

==========
[MERGE TO M52] Don't recreate the speech encoder if we don't have to

If the specification for the speech encoder hasn't changed, we should
reuse it instead of recreating it. Otherwise, we lose its state. (This
problem was originally discovered because AudioEncoderOpus instances
would forget that they were supposed to be using DTX.)

BUG=webrtc:6020, chromium:622647

Review-Url: https://codereview.webrtc.org/2089183002
Cr-Commit-Position: refs/heads/master@{#13273}
(cherry picked from commit 3f81fcd2e845505c2873c7ec2edade910213596b)

Committed:
https://chromium.googlesource.com/external/webrtc/+/15a5d9f9e3e4e8591c7a598c3...
==========

[hlundin-webrtc, 2016-06-29 08:27:34]

Committed patchset #1 (id:1) manually as
15a5d9f9e3e4e8591c7a598c3818f42987cff522.