The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/53230708edb532cd8701917a3435e888b36f6928

commit 53230708edb532cd8701917a3435e888b36f6928
Author: Sammie Quon <sammiequon@google.com>
Date: Mon Sep 17 19:10:08 2018

overview: Introduce swipe up on shelf to hide overview mode.

Show launcher when overview is hidden. Overview is slowly fading
away as the launcher comes in, so on release if overview is to be
hidden, we do not need any of the previous ending animations, so
introduce a new exit animation type.

Fades and slides out overview by transforming the overview grid's
shield widget and each window and its item widget (the title bar,
background, and close button). There is a animation on gesture
release. Normal overview exit animations are skipped and overview
will be shutdown without animations afterwards.

Left a couple TODO for follow up patch as this cl was getting large.

Test: ash_unittests HomeLauncherGestureHandlerTest.OverviewMode
Bug:  883536 
Change-Id: I476e3974faaa991c2195418cc19a24029a4fecc4
Reviewed-on: https://chromium-review.googlesource.com/1222878
Commit-Queue: Sammie Quon <sammiequon@chromium.org>
Reviewed-by: Xiaoqian Dai <xdai@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#591764}
[modify] https://crrev.com/53230708edb532cd8701917a3435e888b36f6928/ash/app_list/app_list_controller_impl.cc
[modify] https://crrev.com/53230708edb532cd8701917a3435e888b36f6928/ash/app_list/app_list_controller_impl.h
[modify] https://crrev.com/53230708edb532cd8701917a3435e888b36f6928/ash/app_list/app_list_presenter_delegate_unittest.cc
[modify] https://crrev.com/53230708edb532cd8701917a3435e888b36f6928/ash/app_list/home_launcher_gesture_handler.cc
[modify] https://crrev.com/53230708edb532cd8701917a3435e888b36f6928/ash/app_list/home_launcher_gesture_handler.h
[modify] https://crrev.com/53230708edb532cd8701917a3435e888b36f6928/ash/app_list/home_launcher_gesture_handler_unittest.cc
[modify] https://crrev.com/53230708edb532cd8701917a3435e888b36f6928/ash/app_list/presenter/app_list_presenter_impl.cc
[modify] https://crrev.com/53230708edb532cd8701917a3435e888b36f6928/ash/app_list/presenter/app_list_presenter_impl.h
[modify] https://crrev.com/53230708edb532cd8701917a3435e888b36f6928/ash/shelf/app_list_shelf_item_delegate.cc
[modify] https://crrev.com/53230708edb532cd8701917a3435e888b36f6928/ash/wm/overview/window_grid.cc
[modify] https://crrev.com/53230708edb532cd8701917a3435e888b36f6928/ash/wm/overview/window_grid.h
[modify] https://crrev.com/53230708edb532cd8701917a3435e888b36f6928/ash/wm/overview/window_selector.cc
[modify] https://crrev.com/53230708edb532cd8701917a3435e888b36f6928/ash/wm/overview/window_selector.h
[modify] https://crrev.com/53230708edb532cd8701917a3435e888b36f6928/ash/wm/overview/window_selector_controller.cc
[modify] https://crrev.com/53230708edb532cd8701917a3435e888b36f6928/ash/wm/overview/window_selector_controller.h
[modify] https://crrev.com/53230708edb532cd8701917a3435e888b36f6928/ash/wm/overview/window_selector_item.cc
[modify] https://crrev.com/53230708edb532cd8701917a3435e888b36f6928/ash/wm/overview/window_selector_item.h
[modify] https://crrev.com/53230708edb532cd8701917a3435e888b36f6928/ash/wm/overview/window_selector_unittest.cc