https://chromium-review.googlesource.com/c/chromium/src/+/1105021

This bug requires manual review: M68 has already been promoted to the beta branch, so this requires manual review
Please contact the milestone owner if you have questions.
Owners: cmasso@(Android), kariahda@(iOS), bhthompson@(ChromeOS), abdulsyed@(Desktop)

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The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a272f89037041cbfb4fae2a4456e68052c6b287c

commit a272f89037041cbfb4fae2a4456e68052c6b287c
Author: Ryan Landay <rlanday@chromium.org>
Date: Mon Jun 18 22:37:12 2018

Fix blank tabs during scrolling in Android horizontal tab switcher

In the Android horizontal tab switcher, we determine which tab thumbnails to
render based on the index of the currently-centered tab, as determined by
NonOverlappingStack#computeReferenceIndex() (this is a virtual method called by
Stack since the logic for updating visibility is shared between the overlapping
and non-overlapping tab switchers). We currently have a bug where the tab
thumbnails are becoming blank during quick scrolling. This is because the
current implementation of this method uses mScrollTarget instead of
mScrollOffset to determine the centered tab (basically, mScrollTarget is where
we're going and mScrollOffset is where we are, and is actually used for
rendering).

This CL fixes this bug by updating this method's implementation to use the value
returned from getCenteredTabIndex(), which uses mScrollOffset instead of
mScrollTarget.

Bug:  853879 ,831359
Change-Id: I129c03ca80297c15b670d223bfc6630b6d8de68c
Reviewed-on: https://chromium-review.googlesource.com/1105021
Reviewed-by: Matthew Jones <mdjones@chromium.org>
Commit-Queue: Ryan Landay <rlanday@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568203}
[modify] https://crrev.com/a272f89037041cbfb4fae2a4456e68052c6b287c/chrome/android/java/src/org/chromium/chrome/browser/compositor/layouts/phone/stack/NonOverlappingStack.java

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/40c80d392aca9d9f282550c6e2f603942b589e97

commit 40c80d392aca9d9f282550c6e2f603942b589e97
Author: Ryan Landay <rlanday@chromium.org>
Date: Thu Jun 21 16:09:40 2018

Fix blank tabs during scrolling in Android horizontal tab switcher

In the Android horizontal tab switcher, we determine which tab thumbnails to
render based on the index of the currently-centered tab, as determined by
NonOverlappingStack#computeReferenceIndex() (this is a virtual method called by
Stack since the logic for updating visibility is shared between the overlapping
and non-overlapping tab switchers). We currently have a bug where the tab
thumbnails are becoming blank during quick scrolling. This is because the
current implementation of this method uses mScrollTarget instead of
mScrollOffset to determine the centered tab (basically, mScrollTarget is where
we're going and mScrollOffset is where we are, and is actually used for
rendering).

This CL fixes this bug by updating this method's implementation to use the value
returned from getCenteredTabIndex(), which uses mScrollOffset instead of
mScrollTarget.

Bug:  853879 ,831359
Change-Id: I129c03ca80297c15b670d223bfc6630b6d8de68c
Reviewed-on: https://chromium-review.googlesource.com/1105021
Reviewed-by: Matthew Jones <mdjones@chromium.org>
Commit-Queue: Ryan Landay <rlanday@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#568203}(cherry picked from commit a272f89037041cbfb4fae2a4456e68052c6b287c)
Reviewed-on: https://chromium-review.googlesource.com/1110277
Reviewed-by: Ryan Landay <rlanday@chromium.org>
Cr-Commit-Position: refs/branch-heads/3440@{#472}
Cr-Branched-From: 010ddcfda246975d194964ccf20038ebbdec6084-refs/heads/master@{#561733}
[modify] https://crrev.com/40c80d392aca9d9f282550c6e2f603942b589e97/chrome/android/java/src/org/chromium/chrome/browser/compositor/layouts/phone/stack/NonOverlappingStack.java

Didn't see any blank issues while scrolling.
Tested on: Sony Xperia M4 Aqua (E2306) / 6.0.1