Fix Views overlay scrollbar border stroke.

Fix Views overlay scrollbar border stroke.

Using a square end cap instead of "butt" makes the stroke extend by a
half stroke width (0.5dp or 1px @2x) at the ends.

BUG=702744
Review-Url: https://codereview.chromium.org/2766773002
Cr-Commit-Position: refs/heads/master@{#458493}
(cherry picked from commit c6359868104299cc1eb5fe2700a792d52ecaac6c)

Review-Url: https://codereview.chromium.org/2767283002 .
Cr-Commit-Position: refs/branch-heads/3029@{#373}
Cr-Branched-From: 939b32ee5ba05c396eef3fd992822fcca9a2e262-refs/heads/master@{#454471}
Committed: https://chromium.googlesource.com/chromium/src/+/277ab19519d29af451139a650fae93da179cc2a0

[Evan Stade, 2017-03-22 22:46:56]

Description was changed from

==========
Fix Views overlay scrollbar border stroke.

Using a square end cap instead of "butt" makes the stroke extend by a
half stroke width (0.5dp or 1px @2x) at the ends.

BUG=702744

Review-Url: https://codereview.chromium.org/2766773002
Cr-Commit-Position: refs/heads/master@{#458493}
(cherry picked from commit c6359868104299cc1eb5fe2700a792d52ecaac6c)
==========

to

==========
Fix Views overlay scrollbar border stroke.

Using a square end cap instead of "butt" makes the stroke extend by a
half stroke width (0.5dp or 1px @2x) at the ends.

BUG=702744

Review-Url: https://codereview.chromium.org/2766773002
Cr-Commit-Position: refs/heads/master@{#458493}
(cherry picked from commit c6359868104299cc1eb5fe2700a792d52ecaac6c)

Review-Url: https://codereview.chromium.org/2767283002 .
Cr-Commit-Position: refs/branch-heads/3029@{#373}
Cr-Branched-From:
939b32ee5ba05c396eef3fd992822fcca9a2e262-refs/heads/master@{#454471}
Committed:
https://chromium.googlesource.com/chromium/src/+/277ab19519d29af451139a650fae...
==========

[Evan Stade, 2017-03-22 22:46:57]

Committed patchset #1 (id:1) manually as
277ab19519d29af451139a650fae93da179cc2a0.