Use a black backdrop for Luminosity SMasks when /BC is missing

[calixteman]

It fixes #21346.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.42%. Comparing base (03eda70) to head (a33e06c).
⚠️ Report is 4 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #21348   +/-   ##
=======================================
  Coverage   81.42%   81.42%           
=======================================
  Files         257      257           
  Lines       65351    65353    +2     
=======================================
+ Hits        53210    53215    +5     
+ Misses      12141    12138    -3     

Flag	Coverage Δ
fonttest	9.10% <ø> (ø)
integrationtest	67.00% <100.00%> (-0.01%)	⬇️
unittest	56.87% <50.00%> (-0.01%)	⬇️
unittestcli	56.07% <50.00%> (-0.03%)	⬇️

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[calixteman]

/botio browsertest

[moz-tools-bot]

From: Bot.io (Windows)

---

Received

Command cmd_browsertest from @calixteman received. Current queue size: 0

Live output at: http://54.193.163.58:8877/1a60137fb3c21c9/output.txt

[moz-tools-bot]

From: Bot.io (Linux m4)

---

Received

Command cmd_browsertest from @calixteman received. Current queue size: 0

Live output at: http://54.241.84.105:8877/17a9485e9cec5df/output.txt

[moz-tools-bot]

From: Bot.io (Linux m4)

---

Failed

Full output at http://54.241.84.105:8877/17a9485e9cec5df/output.txt

Total script time: 19.33 mins

• Regression tests: FAILED

  different ref/snapshot: 7

Image differences available at: http://54.241.84.105:8877/17a9485e9cec5df/reftest-analyzer.html#web=eq.log

[moz-tools-bot]

From: Bot.io (Windows)

---

Failed

Full output at http://54.193.163.58:8877/1a60137fb3c21c9/output.txt

Total script time: 26.90 mins

• Regression tests: FAILED

  different ref/snapshot: 7

Image differences available at: http://54.193.163.58:8877/1a60137fb3c21c9/reftest-analyzer.html#web=eq.log

[timvandermeij]

Thank you for fixing this!

/botio makeref

[moz-tools-bot]

From: Bot.io (Linux m4)

---

Received

Command cmd_makeref from @timvandermeij received. Current queue size: 0

Live output at: http://54.241.84.105:8877/5d1781214533f64/output.txt

[moz-tools-bot]

From: Bot.io (Windows)

---

Received

Command cmd_makeref from @timvandermeij received. Current queue size: 0

Live output at: http://54.193.163.58:8877/49d57403554bbdf/output.txt

[moz-tools-bot]

From: Bot.io (Linux m4)

---

Success

Full output at http://54.241.84.105:8877/5d1781214533f64/output.txt

Total script time: 18.36 mins

• Make references: Passed
• Check references: Passed

[moz-tools-bot]

From: Bot.io (Windows)

---

Success

Full output at http://54.193.163.58:8877/49d57403554bbdf/output.txt

Total script time: 25.55 mins

• Make references: Passed
• Check references: Passed