Manual Regression Range:
Good Build: 55.0.2871.0
Bad Build: 55.0.2873.0

Deleted: crbug_dd.png 122 KB

	crbug_dd.png 122 KB View Download

Using the per-revision bisect providing the bisect results,
Good build: 55.0.2871.0 (Revision: 420831).
Bad build: 55.0.2873.0 (Revision: 421052).

You are probably looking for a change made after 420954 (known good), but no later than 420955 (first known bad).
CHANGELOG URL:
  https://chromium.googlesource.com/chromium/src/+log/38d12538c8af0b8afbf9c5b586b10902b9ba1303..ef06887f125941e96ab19fba834d9027d36d4c88

Adding RB Label as this is a recent Regression.
@schenney -- Could you please look into the issue, pardon me if it has nothing to do with your changes and if possible please assign it to concern owner.
Thank You.

The border is missing - we're not otherwise failing. My patch is a plausible candidate. I'll look into it.

Just to update:

The issue is still seen on mac 10.11.6 latest canary 55.0.2880.4 - Bottom of the drop down menu appear chopped

Yes, we're aware it still exists. Note that the menu is not actually chopped off. The issue is a missing border.

 Issue 651344  has been merged into this issue.

 Issue 653494  has been merged into this issue.

 Issue 653847  has been merged into this issue.

We are snapping sub-pixel sizes down to ints resulting in layers that are too small. Here the border is being cut off. In other cases the background bleeds through.

Gentle Ping! M55 will be pushed to stable soon, Could anyone let us know is there any latest update available for this issue ? 

The feature that caused the bug has been disabled for m55 (or will be very shortly). I've moved the milestone to m56 and I'll be looking at it today.

Reduced test case. Seems like we're snapping the border differently to the layer size. Intersting that we do show the bottom border when scrolled all the way down.

Deleted: border-on-fractional-sized-scroller.html 339 bytes

border-on-fractional-sized-scroller.html 339 bytes View Download

I think the problem is with the clip rect for the scrolling layer being too tall. That explains why the border is visible when the scroller is all the way up (because there is no more of the scroller to clip). If we always round clip rects up, we'll have this problem.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c8338128808d2dae2ffc77a87a47554eeb7d4210

commit c8338128808d2dae2ffc77a87a47554eeb7d4210
Author: Robert Flack <flackr@chromium.org>
Date: Sat Oct 22 02:32:15 2016

Make CompositeOpaqueScrollers experimental until  https://crbug.com/644833  is fixed.

BUG= 644833 , 651305 

Review-Url: https://chromiumcodereview.appspot.com/2439573002
Cr-Commit-Position: refs/heads/master@{#426486}
(cherry picked from commit 42f45334458475b43440671e6e7de5ff95e54a7c)

Review URL: https://codereview.chromium.org/2444663002 .

Cr-Commit-Position: refs/branch-heads/2883@{#235}
Cr-Branched-From: 614d31daee2f61b0180df403a8ad43f20b9f6dd7-refs/heads/master@{#423768}

[modify] https://crrev.com/c8338128808d2dae2ffc77a87a47554eeb7d4210/third_party/WebKit/Source/platform/RuntimeEnabledFeatures.in

Verified this issue on chrome latest Dev M55-55.0.2883.25 by following steps mentioned in the original comment. Observed the bottom border of the drop down menu is visible as expected. Hence adding TE-Verified label.

Deleted: Screen Shot 2016-10-24 at 3.39.41 PM.png 252 KB

	Screen Shot 2016-10-24 at 3.39.41 PM.png 252 KB View Download

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/10336a25975c113e068268d848b01f0c3563f215

commit 10336a25975c113e068268d848b01f0c3563f215
Author: flackr <flackr@chromium.org>
Date: Mon Oct 24 20:27:38 2016

Reenable CompositeOpaqueScrollers on tip of tree.

BUG= 644833 , 651305 

Review-Url: https://codereview.chromium.org/2450473002
Cr-Commit-Position: refs/heads/master@{#427136}

[modify] https://crrev.com/10336a25975c113e068268d848b01f0c3563f215/third_party/WebKit/Source/platform/RuntimeEnabledFeatures.in

Tested the issue on Windows 7, Linux Ubuntu 14.04 and Mac 10.11.6 using chrome version 56.0.2900.0.Still seeing the drop down border is invisible.

flackr@ could you please find the attached screen shot and confirm on the fix.

Thanks,

Deleted: 651305.png 201 KB

	651305.png 201 KB View Download

As per comment #12, we disabled the CompositeOpaqueScrollers feature in M55 but we are planning on fixing it for M56, so we still need https://codereview.chromium.org/2442833002 to land for this bug.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ecd9fdae8684493203bc19683c83da02e397512c

commit ecd9fdae8684493203bc19683c83da02e397512c
Author: schenney <schenney@chromium.org>
Date: Tue Oct 25 18:05:26 2016

Fix the overflow clip rect rounding for overflow scrolling

We were using the enclosingIntRect, but that sets the clip too
large and enables the scrolling contents to paint over the
container's border. Switch to using the pixelSnappedIntRect
to correctly size the clip to the scrolling layer.

Update a test to catch this case in addition to the existing
fractionally sized layer issues.

Fix a potential source of problems in computing scroll offsets
due to different methods for computing contentsSize.

R=flackr@chromium.org
BUG= 651305 
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2

Review-Url: https://codereview.chromium.org/2442833002
Cr-Commit-Position: refs/heads/master@{#427411}

[modify] https://crrev.com/ecd9fdae8684493203bc19683c83da02e397512c/third_party/WebKit/LayoutTests/compositing/overflow/fractional-sized-scrolling-layer-expected.png
[modify] https://crrev.com/ecd9fdae8684493203bc19683c83da02e397512c/third_party/WebKit/LayoutTests/compositing/overflow/fractional-sized-scrolling-layer-expected.txt
[modify] https://crrev.com/ecd9fdae8684493203bc19683c83da02e397512c/third_party/WebKit/LayoutTests/compositing/overflow/fractional-sized-scrolling-layer.html
[modify] https://crrev.com/ecd9fdae8684493203bc19683c83da02e397512c/third_party/WebKit/LayoutTests/virtual/prefer_compositing_to_lcd_text/compositing/overflow/fractional-sized-scrolling-layer-expected.png
[modify] https://crrev.com/ecd9fdae8684493203bc19683c83da02e397512c/third_party/WebKit/LayoutTests/virtual/prefer_compositing_to_lcd_text/compositing/overflow/fractional-sized-scrolling-layer-expected.txt
[modify] https://crrev.com/ecd9fdae8684493203bc19683c83da02e397512c/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
[modify] https://crrev.com/ecd9fdae8684493203bc19683c83da02e397512c/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
[modify] https://crrev.com/ecd9fdae8684493203bc19683c83da02e397512c/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp

Verified the issue on windows 10, Ubuntu 14.04 and Mac 10.11.6 using chrome dev version #56.0.2902.0 as per the comment #0 and #1

Observed that the fix is working as expected.

Attaching screencast for reference

Hence, adding the verified labels.

Deleted: 651305.ogv 1.6 MB

	651305.ogv 1.6 MB View Download

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c8338128808d2dae2ffc77a87a47554eeb7d4210

commit c8338128808d2dae2ffc77a87a47554eeb7d4210
Author: Robert Flack <flackr@chromium.org>
Date: Sat Oct 22 02:32:15 2016

Make CompositeOpaqueScrollers experimental until  https://crbug.com/644833  is fixed.

BUG= 644833 , 651305 

Review-Url: https://chromiumcodereview.appspot.com/2439573002
Cr-Commit-Position: refs/heads/master@{#426486}
(cherry picked from commit 42f45334458475b43440671e6e7de5ff95e54a7c)

Review URL: https://codereview.chromium.org/2444663002 .

Cr-Commit-Position: refs/branch-heads/2883@{#235}
Cr-Branched-From: 614d31daee2f61b0180df403a8ad43f20b9f6dd7-refs/heads/master@{#423768}

[modify] https://crrev.com/c8338128808d2dae2ffc77a87a47554eeb7d4210/third_party/WebKit/Source/platform/RuntimeEnabledFeatures.in

[Automated comment] removing mislabelled merge-merged-2840

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/318d3c7d33df6e1c6a16d929a57d350f77acfd91

commit 318d3c7d33df6e1c6a16d929a57d350f77acfd91
Author: Eric Willigers <ericwilligers@chromium.org>
Date: Wed Aug 08 17:22:16 2018

Retire CompositeOpaqueScrollers flag

CompositeOpaqueScrollers has been shipping since M56.
https://codereview.chromium.org/2450473002

BUG= 644833 ,  651305 

Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I2efd8b92d96177ebfa45b360c02a5cf5e31a18dc
Reviewed-on: https://chromium-review.googlesource.com/1166611
Reviewed-by: Robert Flack <flackr@chromium.org>
Commit-Queue: Eric Willigers <ericwilligers@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581610}
[modify] https://crrev.com/318d3c7d33df6e1c6a16d929a57d350f77acfd91/third_party/WebKit/LayoutTests/compositing/overflow/overflow-scroll-background-opaque-to-transparent.html
[modify] https://crrev.com/318d3c7d33df6e1c6a16d929a57d350f77acfd91/third_party/WebKit/LayoutTests/compositing/overflow/overflow-scroll-background-transparent-to-opaque.html
[modify] https://crrev.com/318d3c7d33df6e1c6a16d929a57d350f77acfd91/third_party/WebKit/LayoutTests/compositing/overflow/overflow-scroll-with-opaque-background.html
[modify] https://crrev.com/318d3c7d33df6e1c6a16d929a57d350f77acfd91/third_party/blink/renderer/core/paint/compositing/compositing_reason_finder_test.cc
[modify] https://crrev.com/318d3c7d33df6e1c6a16d929a57d350f77acfd91/third_party/blink/renderer/core/paint/paint_layer_scrollable_area.cc
[modify] https://crrev.com/318d3c7d33df6e1c6a16d929a57d350f77acfd91/third_party/blink/renderer/core/paint/paint_layer_scrollable_area_test.cc
[modify] https://crrev.com/318d3c7d33df6e1c6a16d929a57d350f77acfd91/third_party/blink/renderer/platform/runtime_enabled_features.json5