Cleanup the remaining references to source_view_id

Cleanup the remaining references to source_view_id

BUG=473258
When Android webview implemented message ports, it set the source frame
to target frame simply to be able transfer message ports, as blink
required a valid source frame. Now the requirement is gone, cleanup
the logic.

Committed: https://crrev.com/b7dd90bc849f4f3eebfdf0a5ad72b275104a4483
Cr-Commit-Position: refs/heads/master@{#344302}

[sgurun-gerrit only, 2015-08-19 01:12:19]

sgurun@chromium.org changed reviewers:
+ nasko@chromium.org

[sgurun-gerrit only, 2015-08-19 01:12:37]

On 2015/08/19 01:12:19, sgurun wrote:
> mailto:sgurun@chromium.org changed reviewers:
> + mailto:nasko@chromium.org

nasko@ ptal, this is the bonus cleanup CL

[nasko, 2015-08-19 16:44:45]

nasko@chromium.org changed reviewers:
+ alexmos@chromium.org

[nasko, 2015-08-19 16:44:45]

Adding alexmos@, as he has done most of the work on postMessage to double check
me :).

LGTM

[alexmos, 2015-08-19 16:56:06]

LGTM, thanks for the cleanup!  I've started the linux_site_isolation trybot to
also double-check the postMessage tests with --site-per-process.

[sgurun-gerrit only, 2015-08-19 17:43:33]

On 2015/08/19 16:56:06, alexmos wrote:
> LGTM, thanks for the cleanup!  I've started the linux_site_isolation trybot to
> also double-check the postMessage tests with --site-per-process.

thanks!

[sgurun-gerrit only, 2015-08-19 17:43:49]

The CQ bit was checked by sgurun@chromium.org

[commit-bot: I haz the power, 2015-08-19 17:44:39]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1297993005/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1297993005/1

[commit-bot: I haz the power, 2015-08-19 19:23:52]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-08-19 19:24:55]

Patchset 1 (id:??) landed as
https://crrev.com/b7dd90bc849f4f3eebfdf0a5ad72b275104a4483
Cr-Commit-Position: refs/heads/master@{#344302}