C87 regression - button shape

[LaurenWags]

Description

In some places the button shape is not correct. See below for 2 examples of where buttons on a bubble are not the same shape as they were on 1.16.x/C86

Steps to Reproduce

1. Clean profile 1.18.x w/ C87
2. Navigate to reddit.com --> look at bubble asking to Show Notifications
3. Navigate to 3zsistemi.si --> look at bubble offering Google Translate installation

Actual result:

Buttons are rectangular

Expected result:

Buttons to be pill shaped

Reproduces how often:

Brave version (brave://version info)

Brave	1.18.18 Chromium: 87.0.4280.27 (Official Build) nightly (x86_64)
Revision	d8c1fe98de8d9c6bd46ebe8b0cc9d2b6bdccca1e-refs/branch-heads/4280@{#556}
OS	macOS Version 10.14.6 (Build 18G6032)

Version/Channel Information:

• Can you reproduce this issue with the current release? no 1.16.x
• Can you reproduce this issue with the beta channel? no 1.17.x
• Can you reproduce this issue with the nightly channel? yes 1.18.x

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields?
• Does the issue resolve itself when disabling Brave Rewards?
• Is the issue reproducible on the latest version of Chrome?

Miscellaneous Information:

cc @mkarolin @rebron

[GeetaSarvadnya]

button shape is not as per the brave brand. Pages which doesn't have the brave branded shapes are listed below:

Edit bookmarks buttons:

Cookies in Use:

[bbondy]

Please do not assign milestones until issues are closed. If this is release blocking though it can stay but add a release/blocking label.

https://github.com/brave/brave-browser/wiki/Triage-Guidelines#milestones-and-issues

[LaurenWags]

Verified passed with

Brave | 1.17.63 Chromium: 87.0.4280.49 (Official Build) unknown (x86_64)
-- | --
Revision | f77f85899646b42a1d3c8ff36794e00becab9171-refs/branch-heads/4280@{#1115}
OS | macOS Version 10.14.6 (Build 18G6032)

Verified expected button shape on screens mentioned in #12418 (comment)

Screenshots

Verified expected button shape on screens mentioned in #12418 (comment)

Screenshots

---

Verified passed with

Brave	1.17.63 Chromium: 87.0.4280.49 (Official Build) dev (64-bit)
Revision	f77f85899646b42a1d3c8ff36794e00becab9171-refs/branch-heads/4280@{#1115}
OS	Windows 7 Service Pack 1 (Build 7601.24544)

Verified STR from description

Verified expected button shape on screens mentioned in #12418 (comment)

Screenshots

Verified expected button shape on screens mentioned in #12418 (comment)

Screenshots

---

Verification passed on

Brave	1.17.63 Chromium: 87.0.4280.49 (Official Build) dev (64-bit)
Revision	f77f85899646b42a1d3c8ff36794e00becab9171-refs/branch-heads/4280@{#1115}
OS	Ubuntu 18.04 LTS

Verified STR from description

Verified expected button shape on screens mentioned in #12418 (comment)

Screenshots

Verified expected button shape on screens mentioned in #12418 (comment)

Screenshots