Should we have the linear fade in when scrolling as well? Or just on hover?

Just on hover.

Thanks. BTW, any reason to keep this RVG when all the other bugs (including launch bug) are public?

Sorry just a reflex :)

sgabriel@ Do we need fade in animation for scrolling appear? 

Today the thumb abruptly appears when the user hovers the invisible scrollbar area for 1s delay. Do we introduce this (0.2s) animation after 1s delay?

Scrolling remains un-changed, it appears right away.
Hovering invisible scrollbar fade-in the expanded thumb over 0.2s after the 1s delay.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a47e7158e746c01b4ccbbd25d71e267d93347b94

commit a47e7158e746c01b4ccbbd25d71e267d93347b94
Author: chaopeng <chaopeng@chromium.org>
Date: Mon Apr 24 20:26:54 2017

change overlay scrollbar hover show to hover fade in

Currently, we have 2 ways to show the hidden scrollbars:

1. scroll position update
2. move mouse to a region near edge

In this patch, we only change the "move mouse to a region near edge" to
show scrollbars immediately to fade in scrollbars.

BUG= 710543 
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel

Review-Url: https://codereview.chromium.org/2816923002
Cr-Commit-Position: refs/heads/master@{#466740}

[modify] https://crrev.com/a47e7158e746c01b4ccbbd25d71e267d93347b94/cc/input/scrollbar_animation_controller.cc
[modify] https://crrev.com/a47e7158e746c01b4ccbbd25d71e267d93347b94/cc/input/scrollbar_animation_controller.h
[modify] https://crrev.com/a47e7158e746c01b4ccbbd25d71e267d93347b94/cc/input/scrollbar_animation_controller_unittest.cc
[modify] https://crrev.com/a47e7158e746c01b4ccbbd25d71e267d93347b94/cc/layers/scrollbar_layer_unittest.cc
[modify] https://crrev.com/a47e7158e746c01b4ccbbd25d71e267d93347b94/cc/trees/layer_tree_host_impl_unittest.cc
[modify] https://crrev.com/a47e7158e746c01b4ccbbd25d71e267d93347b94/cc/trees/layer_tree_impl.cc
[modify] https://crrev.com/a47e7158e746c01b4ccbbd25d71e267d93347b94/cc/trees/layer_tree_settings.h
[modify] https://crrev.com/a47e7158e746c01b4ccbbd25d71e267d93347b94/content/child/webthemeengine_impl_default.cc
[modify] https://crrev.com/a47e7158e746c01b4ccbbd25d71e267d93347b94/content/renderer/gpu/render_widget_compositor.cc
[modify] https://crrev.com/a47e7158e746c01b4ccbbd25d71e267d93347b94/ui/native_theme/overlay_scrollbar_constants_aura.h
[modify] https://crrev.com/a47e7158e746c01b4ccbbd25d71e267d93347b94/ui/views/controls/scrollbar/overlay_scroll_bar.cc

Fix confirmed in latest Canary. Requesting merge to 59.

Your change meets the bar and is auto-approved for M59. Please go ahead and merge the CL to branch 3071 manually. Please contact milestone owner if you have questions.
Owners: amineer@(Android), cmasso@(iOS), gkihumba@(ChromeOS), Abdul Syed@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/28eee7a896dd8299e53d555e2232e6422ceb8a5e

commit 28eee7a896dd8299e53d555e2232e6422ceb8a5e
Author: David Bokan <bokan@chromium.org>
Date: Fri Apr 28 21:15:39 2017

change overlay scrollbar hover show to hover fade in

Currently, we have 2 ways to show the hidden scrollbars:

1. scroll position update
2. move mouse to a region near edge

In this patch, we only change the "move mouse to a region near edge" to
show scrollbars immediately to fade in scrollbars.

BUG= 710543 
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel

Review-Url: https://codereview.chromium.org/2816923002
Cr-Commit-Position: refs/heads/master@{#466740}
(cherry picked from commit a47e7158e746c01b4ccbbd25d71e267d93347b94)

Review-Url: https://codereview.chromium.org/2843293004 .
Cr-Commit-Position: refs/branch-heads/3071@{#303}
Cr-Branched-From: a106f0abbf69dad349d4aaf4bcc4f5d376dd2377-refs/heads/master@{#464641}

[modify] https://crrev.com/28eee7a896dd8299e53d555e2232e6422ceb8a5e/cc/input/scrollbar_animation_controller.cc
[modify] https://crrev.com/28eee7a896dd8299e53d555e2232e6422ceb8a5e/cc/input/scrollbar_animation_controller.h
[modify] https://crrev.com/28eee7a896dd8299e53d555e2232e6422ceb8a5e/cc/input/scrollbar_animation_controller_unittest.cc
[modify] https://crrev.com/28eee7a896dd8299e53d555e2232e6422ceb8a5e/cc/layers/scrollbar_layer_unittest.cc
[modify] https://crrev.com/28eee7a896dd8299e53d555e2232e6422ceb8a5e/cc/trees/layer_tree_host_impl_unittest.cc
[modify] https://crrev.com/28eee7a896dd8299e53d555e2232e6422ceb8a5e/cc/trees/layer_tree_impl.cc
[modify] https://crrev.com/28eee7a896dd8299e53d555e2232e6422ceb8a5e/cc/trees/layer_tree_settings.h
[modify] https://crrev.com/28eee7a896dd8299e53d555e2232e6422ceb8a5e/content/child/webthemeengine_impl_default.cc
[modify] https://crrev.com/28eee7a896dd8299e53d555e2232e6422ceb8a5e/content/renderer/gpu/render_widget_compositor.cc
[modify] https://crrev.com/28eee7a896dd8299e53d555e2232e6422ceb8a5e/ui/native_theme/overlay_scrollbar_constants_aura.h
[modify] https://crrev.com/28eee7a896dd8299e53d555e2232e6422ceb8a5e/ui/views/controls/scrollbar/overlay_scroll_bar.cc

Ok, just merged this back to 59. The merge had a few conflicts as there was a big rename in the mean time, I think I got it right but just in case +dtapuska@, if this needs to get kicked out or hits trouble otherwise, mind taking care of it while I'm OOO? (I'll monitor betabuilders the rest of tonight)

Ya I can deal with fallout if need be :-|

ChromeOS 9460.30.0 / 59.0.3071.41 . Verified fade in scrollbar for mouse hover case