I still can't reproduce this. That likely means the reproductions you're giving are not all that's needed to trigger the behavior. What else did you do before? Are you seeing this all the time?

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d64d9854a1d22208db2d97b7f441696ed0ca8fa0

commit d64d9854a1d22208db2d97b7f441696ed0ca8fa0
Author: dtseng <dtseng@chromium.org>
Date: Wed Mar 29 20:27:23 2017

Ensure only one instance of AutomationInternalCustomBindings for background page extensions

Previously, if an extension requesting automation has more than one page it opens in its extension process (e.g. background.html and panel.html, in ChromeVox), we instantiated two AutomationInternalCustomBindings (one for each page).

This fix makes it so we only ever make "active" the instance that is associated with the extension's background page.

Note that as a result, any calls to chrome.automation from non-background page contexts will result in an no-op (e.g. getDesktop will not trigger the callback).

In the case that the extension has no background page, we revert to the previous behavior of having one instance per page.

TEST=open the ChromeVox Panel, and close it again. Press caps lock. Verify we only process one event and only output one alert.
BUG= 691165 
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2782753002
Cr-Commit-Position: refs/heads/master@{#460520}

[modify] https://crrev.com/d64d9854a1d22208db2d97b7f441696ed0ca8fa0/chrome/browser/resources/chromeos/chromevox/cvox2/background/panel.js
[modify] https://crrev.com/d64d9854a1d22208db2d97b7f441696ed0ca8fa0/chrome/browser/resources/chromeos/chromevox/cvox2/background/panel_test.extjs
[modify] https://crrev.com/d64d9854a1d22208db2d97b7f441696ed0ca8fa0/chrome/browser/resources/chromeos/chromevox/testing/mock_feedback.js
[modify] https://crrev.com/d64d9854a1d22208db2d97b7f441696ed0ca8fa0/chrome/renderer/extensions/automation_internal_custom_bindings.cc
[modify] https://crrev.com/d64d9854a1d22208db2d97b7f441696ed0ca8fa0/chrome/renderer/extensions/automation_internal_custom_bindings.h

 Issue 656351  has been merged into this issue.