Encrypted Media: Replace web_session_id with session_id

Encrypted Media: Replace web_session_id with session_id

Now we don't have the integer session_id anymore,
there's no need to have a separate name.
So rename web_session_id to session_id.

BUG=440510
R=xhwang@chromium.org

Committed: https://crrev.com/c0b80de1f748956ed744d35c4c884e373dad8a53
Cr-Commit-Position: refs/heads/master@{#317986}

[gunsch, 2015-02-05 16:37:57]

On 2015/02/05 09:26:47, zhuoyu.qian wrote:

xhwang@ can't approve code in chromecast/ :)

chromecast/ lgtm

[xhwang, 2015-02-05 17:51:42]

non-owner lgtm :)

[zhuoyu.qian, 2015-02-06 02:59:42]

zhuoyu.qian@samsung.com changed reviewers:
+ damienv@chromium.org, kolla@chromium.org, lcwu@chromium.org
- xhwang@chromium.org

[zhuoyu.qian, 2015-02-06 02:59:43]

I'd like you to do a code review.  Please visit

    https://codereview.chromium.org/903663002

to have a look.
Thank you.

[zhuoyu.qian, 2015-02-09 09:50:22]

The CQ bit was checked by zhuoyu.qian@samsung.com

[commit-bot: I haz the power, 2015-02-09 09:51:07]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/903663002/1

[commit-bot: I haz the power, 2015-02-09 09:55:56]

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

[commit-bot: I haz the power, 2015-02-09 09:55:57]

Try jobs failed on following builders:
  chromium_presubmit on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/chromium_presub...)

[zhuoyu.qian, 2015-02-25 05:22:08]

The CQ bit was checked by zhuoyu.qian@samsung.com

[commit-bot: I haz the power, 2015-02-25 05:22:37]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/903663002/1

[commit-bot: I haz the power, 2015-02-25 05:28:32]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-25 05:29:25]

Patchset 1 (id:??) landed as
https://crrev.com/c0b80de1f748956ed744d35c4c884e373dad8a53
Cr-Commit-Position: refs/heads/master@{#317986}