Laura here's the bug for overlay scrollbar, feel free to add anything else!

Assigning to Chao to better load-balance remaining work.

Re: Contrast ratio, I we do this on Mac where a dark background causes us to change the color of scrollbars to a lighter shade. I think we should do the same thing here. However, on the provided link, it seems like that's an edge case we can't fix in general, an alternating dark/light background means no single color will work well. Is "best-effort" good enough or is there a standard practice we can follow here?

lpalmaro@, is there anything else we should be thinking about on the accessibility front here? We don't have a lot of time before the shipping date so please take a look soon.

Thanks!

 Issue 299065  has been merged into this issue.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/3386732f6b5e6959698b6697e799a5eb3be6e821

commit 3386732f6b5e6959698b6697e799a5eb3be6e821
Author: chaopeng <chaopeng@chromium.org>
Date: Fri Oct 28 14:49:49 2016

Aura overlay scrollbars adjust color for dark backgrounds

Since we already save the overlay scrollbar color theme in ScrollableArea for
Mac, this patch plumbs it through for Aura overlay scrollbars.

Also we rename ScrollbarOverlayStyle to ScrollbarOverlayColorTheme to avoid
misleading since we already have ScrollbarStyle WebThemeEngine.h.

BUG= 636662 
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2

Review-Url: https://codereview.chromium.org/2426793002
Cr-Commit-Position: refs/heads/master@{#428367}

[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/content/child/webthemeengine_impl_default.cc
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/content/child/webthemeengine_impl_default.h
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/third_party/WebKit/Source/core/frame/FrameView.cpp
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/third_party/WebKit/Source/core/layout/LayoutBox.cpp
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/third_party/WebKit/Source/core/paint/PaintLayerScrollableAreaTest.cpp
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/third_party/WebKit/Source/platform/exported/WebScrollbarImpl.cpp
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/third_party/WebKit/Source/platform/exported/WebScrollbarImpl.h
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/third_party/WebKit/Source/platform/exported/WebScrollbarThemeClientImpl.cpp
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/third_party/WebKit/Source/platform/exported/WebScrollbarThemeClientImpl.h
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/third_party/WebKit/Source/platform/scroll/ScrollTypes.h
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/third_party/WebKit/Source/platform/scroll/ScrollableArea.h
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/third_party/WebKit/Source/platform/scroll/ScrollableAreaTest.cpp
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/third_party/WebKit/Source/platform/scroll/Scrollbar.cpp
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/third_party/WebKit/Source/platform/scroll/Scrollbar.h
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/third_party/WebKit/Source/platform/scroll/ScrollbarTheme.h
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/third_party/WebKit/Source/platform/scroll/ScrollbarThemeAura.cpp
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/third_party/WebKit/Source/platform/scroll/ScrollbarThemeClient.h
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/third_party/WebKit/Source/platform/scroll/ScrollbarThemeMac.h
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/third_party/WebKit/Source/platform/scroll/ScrollbarThemeMac.mm
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/third_party/WebKit/Source/platform/scroll/ScrollbarThemeOverlay.cpp
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/third_party/WebKit/Source/web/AssertMatchingEnums.cpp
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/third_party/WebKit/public/BUILD.gn
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/third_party/WebKit/public/platform/WebScrollbar.h
[add] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/third_party/WebKit/public/platform/WebScrollbarOverlayColorTheme.h
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/third_party/WebKit/public/platform/WebThemeEngine.h
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/ui/native_theme/native_theme.h
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/ui/native_theme/native_theme_aura.cc
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/ui/native_theme/native_theme_aura.h
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/ui/native_theme/native_theme_base.cc
[modify] https://crrev.com/3386732f6b5e6959698b6697e799a5eb3be6e821/ui/native_theme/native_theme_base.h