Remove dead extensions tracking code.

Remove dead extensions tracking code.

In https://codereview.chromium.org/2437863005, page_load_histograms,
which was the only consumer of this code, was removed. Now that the
page_load_histograms code has been removed, this code can be removed as
well.

BUG=657993
Committed: https://crrev.com/69722fddd0f46c528986bfc87897b0f1607e1f26
Cr-Commit-Position: refs/heads/master@{#429418}

[Bryan McQuade, 2016-11-02 13:59:38]

The CQ bit was checked by bmcquade@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-11-02 14:00:04]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[Bryan McQuade, 2016-11-02 14:00:56]

bmcquade@chromium.org changed reviewers:
+ rdevlin.cronin@chromium.org

[Bryan McQuade, 2016-11-02 14:01:36]

Devlin, PTAL - this change removes extension code that is now dead as a result
of removing page_load_histograms. Thanks!

[commit-bot: I haz the power, 2016-11-02 14:52:37]

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

[commit-bot: I haz the power, 2016-11-02 14:52:38]

Dry run: This issue passed the CQ dry run.

[Devlin, 2016-11-02 19:07:37]

lgtm

[Bryan McQuade, 2016-11-02 20:44:18]

The CQ bit was checked by bmcquade@chromium.org

[commit-bot: I haz the power, 2016-11-02 20:45:16]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-11-02 20:55:14]

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

[commit-bot: I haz the power, 2016-11-02 20:55:15]

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

[Bryan McQuade, 2016-11-02 22:00:58]

bmcquade@chromium.org changed reviewers:
+ tsepez@chromium.org

[Bryan McQuade, 2016-11-02 22:01:07]

tsepez, PTAL for 
extensions/common/extension_messages.h change, thanks!

[Tom Sepez, 2016-11-02 22:05:24]

RS LGTM on deleting messages. Thanks for the cleanup.

[Bryan McQuade, 2016-11-02 22:09:45]

The CQ bit was checked by bmcquade@chromium.org

[commit-bot: I haz the power, 2016-11-02 22:10:20]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-11-02 22:16:06]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-11-02 22:20:28]

Description was changed from

==========
Remove dead extensions tracking code.

In https://codereview.chromium.org/2437863005, page_load_histograms,
which was the only consumer of this code, was removed. Now that the
page_load_histograms code has been removed, this code can be removed as
well.

BUG=657993
==========

to

==========
Remove dead extensions tracking code.

In https://codereview.chromium.org/2437863005, page_load_histograms,
which was the only consumer of this code, was removed. Now that the
page_load_histograms code has been removed, this code can be removed as
well.

BUG=657993

Committed: https://crrev.com/69722fddd0f46c528986bfc87897b0f1607e1f26
Cr-Commit-Position: refs/heads/master@{#429418}
==========

[commit-bot: I haz the power, 2016-11-02 22:20:29]

Patchset 2 (id:??) landed as
https://crrev.com/69722fddd0f46c528986bfc87897b0f1607e1f26
Cr-Commit-Position: refs/heads/master@{#429418}