The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f015d425e779da1911a4445941d7cf6411069306

commit f015d425e779da1911a4445941d7cf6411069306
Author: Mohsen Izadi <mohsen@chromium.org>
Date: Fri Oct 26 06:11:39 2018

Remove parallax option from overscroll-history-navigation flag

Simplified gesture-nav has been the default mode for overscroll history
navigation since M66. We can now safely remove parallax mode. This CL
removes the option from the flag and since the flag is now a simple
enable/disable flag, changes it to a feature. Follow-up CLs will remove
the code supporting the deprecated UI.

BUG= 890390 

Change-Id: I92ab3c1da1033853fb12be2a40e4fb4b372e0952
Reviewed-on: https://chromium-review.googlesource.com/c/1272255
Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Commit-Queue: Mohsen Izadi <mohsen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#602997}
[modify] https://crrev.com/f015d425e779da1911a4445941d7cf6411069306/chrome/browser/about_flags.cc
[modify] https://crrev.com/f015d425e779da1911a4445941d7cf6411069306/chrome/browser/flag_descriptions.cc
[modify] https://crrev.com/f015d425e779da1911a4445941d7cf6411069306/chrome/browser/flag_descriptions.h
[modify] https://crrev.com/f015d425e779da1911a4445941d7cf6411069306/content/browser/renderer_host/overscroll_configuration.cc
[modify] https://crrev.com/f015d425e779da1911a4445941d7cf6411069306/content/public/common/content_features.cc
[modify] https://crrev.com/f015d425e779da1911a4445941d7cf6411069306/content/public/common/content_features.h
[modify] https://crrev.com/f015d425e779da1911a4445941d7cf6411069306/content/public/common/content_switches.cc
[modify] https://crrev.com/f015d425e779da1911a4445941d7cf6411069306/content/public/common/content_switches.h
[modify] https://crrev.com/f015d425e779da1911a4445941d7cf6411069306/tools/metrics/histograms/enums.xml

The CL in #14 removes the option for parallax gesture-nav. The undesirable side effect is that gesture-nav would get disabled for those who have set it to parallax. We'll wait another milestone and if everything goes well, we'll remove the code supporting parallax mode.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ac3bb2923c432a36c23bee282c551192db29be33

commit ac3bb2923c432a36c23bee282c551192db29be33
Author: Mohsen Izadi <mohsen@chromium.org>
Date: Sat Dec 22 00:48:07 2018

Removed parallax overscroll code

The parallax overscroll mode is deprecated and the flag to enable it is
already removed in M72. This CL removes unused code for this mode.

BUG= 890390 , 357311 , 399676 , 405945 , 705599 , 701801 , 727718 

Change-Id: I8ab710635e0291dacd8aacdd76c45ffeaf2fac7b
Reviewed-on: https://chromium-review.googlesource.com/c/1273609
Commit-Queue: Mohsen Izadi <mohsen@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Cr-Commit-Position: refs/heads/master@{#618693}
[modify] https://crrev.com/ac3bb2923c432a36c23bee282c551192db29be33/content/browser/BUILD.gn
[modify] https://crrev.com/ac3bb2923c432a36c23bee282c551192db29be33/content/browser/renderer_host/input/touch_selection_controller_client_aura_browsertest.cc
[delete] https://crrev.com/3c771ad0370b97b75b8b623ea301ceb0a44a5208/content/browser/web_contents/aura/overscroll_navigation_overlay.cc
[delete] https://crrev.com/3c771ad0370b97b75b8b623ea301ceb0a44a5208/content/browser/web_contents/aura/overscroll_navigation_overlay.h
[delete] https://crrev.com/3c771ad0370b97b75b8b623ea301ceb0a44a5208/content/browser/web_contents/aura/overscroll_navigation_overlay_unittest.cc
[delete] https://crrev.com/3c771ad0370b97b75b8b623ea301ceb0a44a5208/content/browser/web_contents/aura/overscroll_window_animation.cc
[delete] https://crrev.com/3c771ad0370b97b75b8b623ea301ceb0a44a5208/content/browser/web_contents/aura/overscroll_window_animation.h
[delete] https://crrev.com/3c771ad0370b97b75b8b623ea301ceb0a44a5208/content/browser/web_contents/aura/overscroll_window_animation_unittest.cc
[delete] https://crrev.com/3c771ad0370b97b75b8b623ea301ceb0a44a5208/content/browser/web_contents/aura/overscroll_window_delegate.cc
[delete] https://crrev.com/3c771ad0370b97b75b8b623ea301ceb0a44a5208/content/browser/web_contents/aura/overscroll_window_delegate.h
[delete] https://crrev.com/3c771ad0370b97b75b8b623ea301ceb0a44a5208/content/browser/web_contents/aura/overscroll_window_delegate_unittest.cc
[delete] https://crrev.com/3c771ad0370b97b75b8b623ea301ceb0a44a5208/content/browser/web_contents/aura/shadow_layer_delegate.cc
[delete] https://crrev.com/3c771ad0370b97b75b8b623ea301ceb0a44a5208/content/browser/web_contents/aura/shadow_layer_delegate.h
[modify] https://crrev.com/ac3bb2923c432a36c23bee282c551192db29be33/content/browser/web_contents/web_contents_view_aura.cc
[modify] https://crrev.com/ac3bb2923c432a36c23bee282c551192db29be33/content/browser/web_contents/web_contents_view_aura.h
[modify] https://crrev.com/ac3bb2923c432a36c23bee282c551192db29be33/content/browser/web_contents/web_contents_view_aura_browsertest.cc
[modify] https://crrev.com/ac3bb2923c432a36c23bee282c551192db29be33/content/browser/web_contents/web_contents_view_aura_unittest.cc
[modify] https://crrev.com/ac3bb2923c432a36c23bee282c551192db29be33/content/test/BUILD.gn

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/6e6c40b4697e889533a480fa04ffb2eb96dcda1d

commit 6e6c40b4697e889533a480fa04ffb2eb96dcda1d
Author: Mohsen Izadi <mohsen@chromium.org>
Date: Sat Dec 22 05:49:14 2018

Remove NavigationEntryScreenshotManager

This class is used to take screenshots used in the old gesture-nav UI.
That UI is removed and this class is not used anymore. This CL also
removes the |screenshot_| field from NavigationEntryImpl class.

BUG= 890390 , 170449 , 361594 , 532290 

Change-Id: Ifbee81c058bd165469eb6296f6ca2a47de0355b4
Reviewed-on: https://chromium-review.googlesource.com/c/1274459
Commit-Queue: Mohsen Izadi <mohsen@chromium.org>
Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#618732}
[modify] https://crrev.com/6e6c40b4697e889533a480fa04ffb2eb96dcda1d/chrome/browser/resource_coordinator/tab_manager.cc
[modify] https://crrev.com/6e6c40b4697e889533a480fa04ffb2eb96dcda1d/chrome/browser/resource_coordinator/tab_manager.h
[modify] https://crrev.com/6e6c40b4697e889533a480fa04ffb2eb96dcda1d/content/browser/BUILD.gn
[modify] https://crrev.com/6e6c40b4697e889533a480fa04ffb2eb96dcda1d/content/browser/frame_host/navigation_controller_impl.cc
[modify] https://crrev.com/6e6c40b4697e889533a480fa04ffb2eb96dcda1d/content/browser/frame_host/navigation_controller_impl.h
[modify] https://crrev.com/6e6c40b4697e889533a480fa04ffb2eb96dcda1d/content/browser/frame_host/navigation_controller_impl_unittest.cc
[modify] https://crrev.com/6e6c40b4697e889533a480fa04ffb2eb96dcda1d/content/browser/frame_host/navigation_entry_impl.cc
[modify] https://crrev.com/6e6c40b4697e889533a480fa04ffb2eb96dcda1d/content/browser/frame_host/navigation_entry_impl.h
[delete] https://crrev.com/698bc8aa06fec2bfab1d39c84e37f1646f1d01bf/content/browser/frame_host/navigation_entry_screenshot_manager.cc
[delete] https://crrev.com/698bc8aa06fec2bfab1d39c84e37f1646f1d01bf/content/browser/frame_host/navigation_entry_screenshot_manager.h
[modify] https://crrev.com/6e6c40b4697e889533a480fa04ffb2eb96dcda1d/content/browser/frame_host/navigator_impl.cc
[modify] https://crrev.com/6e6c40b4697e889533a480fa04ffb2eb96dcda1d/content/public/browser/navigation_controller.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/99c4710cc79a70c23c4ecdf2861023a2b254ff9f

commit 99c4710cc79a70c23c4ecdf2861023a2b254ff9f
Author: Mohsen Izadi <mohsen@chromium.org>
Date: Thu Jan 03 08:29:02 2019

Remove HistoryNavigationMode enum

This used to represent three different modes: disabled, simple ui,
parallax ui. Now that the parallax mode is removed, we can use a simple
bool.

BUG= 890390 

Change-Id: Ic96fb6fa82c0fa2f9071e39ef5b0b10af5587e75
Reviewed-on: https://chromium-review.googlesource.com/c/1275205
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Commit-Queue: Mohsen Izadi <mohsen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#619603}
[modify] https://crrev.com/99c4710cc79a70c23c4ecdf2861023a2b254ff9f/chrome/browser/ui/browser.cc
[modify] https://crrev.com/99c4710cc79a70c23c4ecdf2861023a2b254ff9f/content/browser/renderer_host/overscroll_configuration.cc
[modify] https://crrev.com/99c4710cc79a70c23c4ecdf2861023a2b254ff9f/content/browser/renderer_host/render_widget_host_view_aura.cc
[modify] https://crrev.com/99c4710cc79a70c23c4ecdf2861023a2b254ff9f/content/browser/web_contents/web_contents_view_aura.cc
[modify] https://crrev.com/99c4710cc79a70c23c4ecdf2861023a2b254ff9f/content/public/browser/overscroll_configuration.h
[modify] https://crrev.com/99c4710cc79a70c23c4ecdf2861023a2b254ff9f/content/public/test/scoped_overscroll_modes.cc
[modify] https://crrev.com/99c4710cc79a70c23c4ecdf2861023a2b254ff9f/content/public/test/scoped_overscroll_modes.h