[Extensions] Rework inline installation observation

[Extensions] Rework inline installation observation

Instead of observing through the WebstoreAPI, observe directly in the TabHelper.
This is a great deal less code, more direct, and also fixes a lifetime issue
with the TabHelper being deleted before the inline installation completes.

BUG=613949
Review-Url: https://codereview.chromium.org/2103663002
Cr-Commit-Position: refs/heads/master@{#403188}
(cherry picked from commit d30a8bd191f17b61938fc87890bffc80049b0774)

Committed: https://chromium.googlesource.com/chromium/src/+/2bde772815413a04017f6610fae1bc986c0767ba

[Devlin, 2016-07-14 18:03:37]

Description was changed from

==========
[Extensions] Rework inline installation observation

Instead of observing through the WebstoreAPI, observe directly in the TabHelper.
This is a great deal less code, more direct, and also fixes a lifetime issue
with the TabHelper being deleted before the inline installation completes.

BUG=613949

Review-Url: https://codereview.chromium.org/2103663002
Cr-Commit-Position: refs/heads/master@{#403188}
(cherry picked from commit d30a8bd191f17b61938fc87890bffc80049b0774)
==========

to

==========
[Extensions] Rework inline installation observation

Instead of observing through the WebstoreAPI, observe directly in the TabHelper.
This is a great deal less code, more direct, and also fixes a lifetime issue
with the TabHelper being deleted before the inline installation completes.

BUG=613949

Review-Url: https://codereview.chromium.org/2103663002
Cr-Commit-Position: refs/heads/master@{#403188}
(cherry picked from commit d30a8bd191f17b61938fc87890bffc80049b0774)

Committed:
https://chromium.googlesource.com/chromium/src/+/2bde772815413a04017f6610fae1...
==========

[Devlin, 2016-07-14 18:03:38]

Committed patchset #1 (id:1) manually as
2bde772815413a04017f6610fae1bc986c0767ba (tree was closed).