The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9823e58abc9fc8de91f26a31dad7a2d24a8b7727

commit 9823e58abc9fc8de91f26a31dad7a2d24a8b7727
Author: pastarmovj <pastarmovj@chromium.org>
Date: Wed Nov 16 14:18:13 2016

Migrate enabled state of plugins into specialized Flash and PDF prefs.

For PDF and Flash the enabled state is defined by the
ManagedDefaultPluginsSetting and PluginsAlwaysOpenPdfExternally prefs.
All other plugins should never be disabled in the first place.

BUG= 662002 
TEST=manual

Review-Url: https://codereview.chromium.org/2474713003
Cr-Commit-Position: refs/heads/master@{#432477}

[modify] https://crrev.com/9823e58abc9fc8de91f26a31dad7a2d24a8b7727/chrome/browser/plugins/plugin_metadata.cc
[modify] https://crrev.com/9823e58abc9fc8de91f26a31dad7a2d24a8b7727/chrome/browser/plugins/plugin_metadata.h
[modify] https://crrev.com/9823e58abc9fc8de91f26a31dad7a2d24a8b7727/chrome/browser/plugins/plugin_policy_handler.cc
[modify] https://crrev.com/9823e58abc9fc8de91f26a31dad7a2d24a8b7727/chrome/browser/plugins/plugin_prefs.cc
[modify] https://crrev.com/9823e58abc9fc8de91f26a31dad7a2d24a8b7727/tools/metrics/histograms/histograms.xml

@pastarmovj -- Could you please let us know whether the issue can be verified from TE end, if so please help with the steps to verify.
Thank You.

You can verify with the following procedure:

0. Start with a fresh profile.
1. Open the settings page and open the content settings dialog. Verify that the "Open PDF externally" is unchecked and that for Flash the "Enabled" option is selected (don't change them).
2. Navigate to about:plugins and disable the PDF and the Flash plguins.
3. Close the browser and start it again.
4. Open the settings page and open the content settings dialog. Verify that the "Open PDF externally" is *checked* and that for Flash the *"Disabled"* option is selected.
5. Profit!

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/8b32e59714ad13709b8ced2b709e903fcc5caf8e

commit 8b32e59714ad13709b8ced2b709e903fcc5caf8e
Author: pastarmovj <pastarmovj@chromium.org>
Date: Mon Nov 21 15:30:44 2016

Remove obsolete plugin state handling code.

As a byproduct clean up some old Adobe PDF Plugin handling code which
is now obsolete as well.

BUG= 662002 
TEST=unit_tests, browser_tests

Review-Url: https://codereview.chromium.org/2518493002
Cr-Commit-Position: refs/heads/master@{#433549}

[modify] https://crrev.com/8b32e59714ad13709b8ced2b709e903fcc5caf8e/chrome/browser/chrome_plugin_browsertest.cc
[modify] https://crrev.com/8b32e59714ad13709b8ced2b709e903fcc5caf8e/chrome/browser/pdf/pdf_extension_test.cc
[modify] https://crrev.com/8b32e59714ad13709b8ced2b709e903fcc5caf8e/chrome/browser/plugins/plugin_prefs.cc
[modify] https://crrev.com/8b32e59714ad13709b8ced2b709e903fcc5caf8e/chrome/browser/plugins/plugin_prefs.h
[modify] https://crrev.com/8b32e59714ad13709b8ced2b709e903fcc5caf8e/chrome/browser/plugins/plugin_prefs_unittest.cc
[modify] https://crrev.com/8b32e59714ad13709b8ced2b709e903fcc5caf8e/chrome/browser/printing/print_preview_dialog_controller_browsertest.cc
[modify] https://crrev.com/8b32e59714ad13709b8ced2b709e903fcc5caf8e/chrome/browser/ui/BUILD.gn
[modify] https://crrev.com/8b32e59714ad13709b8ced2b709e903fcc5caf8e/chrome/browser/ui/pdf/adobe_reader_info_win.cc
[modify] https://crrev.com/8b32e59714ad13709b8ced2b709e903fcc5caf8e/chrome/browser/ui/pdf/adobe_reader_info_win.h
[modify] https://crrev.com/8b32e59714ad13709b8ced2b709e903fcc5caf8e/chrome/browser/ui/pdf/chrome_pdf_web_contents_helper_client.cc
[delete] https://crrev.com/480941ae30081b194fc34bf4229801636d6d4e5d/chrome/browser/ui/pdf/pdf_unsupported_feature.cc
[delete] https://crrev.com/480941ae30081b194fc34bf4229801636d6d4e5d/chrome/browser/ui/pdf/pdf_unsupported_feature.h
[modify] https://crrev.com/8b32e59714ad13709b8ced2b709e903fcc5caf8e/chrome/browser/ui/webui/plugins/plugins_handler.cc

Followed the steps provided in the Comment# 4 and tested the issue on Windows, Mac and Linux using latest Dev# 56.0.2924.3 and is not reproducible.
Attaching a screen cast of the issue.
@pastarmovj -- Could you please look into the video and confirm so that I can add the appropriate labels.
Thanks in Advance.

Deleted: 662002.mov 9.2 MB

662002.mov 9.2 MB Download

yep all WAI! :)

@pastarmovj -- Thank You for the quick update.
As per Comment# 7 adding TE-Verified Labels.
Thank You.