Add an abstract WasmImage class, that JBig2CCITTFaxImage and JpxImage inherit from

[Snuffleupagus]

Given that these classes are, with the exception of their decode methods, virtually identical this helps reduce code duplication and simplifies maintenance.

These changes reduce the size of the gulp mozcentral build-target by 1292 bytes, which obviously isn't a lot but still cannot hurt.

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Note: This implements the suggestion from #21139 (comment).

[codecov-commenter]

Codecov Report

❌ Patch coverage is 88.33333% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 55.93%. Comparing base (e8d3d19) to head (6ff0f86).

Files with missing lines	Patch %	Lines
src/core/wasm_image.js	85.10%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #21225      +/-   ##
==========================================
- Coverage   55.94%   55.93%   -0.02%     
==========================================
  Files         219      220       +1     
  Lines       59017    58988      -29     
==========================================
- Hits        33020    32992      -28     
+ Misses      25997    25996       -1     

Flag	Coverage Δ
fonttest	8.65% <8.62%> (-0.03%)	⬇️
unittest	55.17% <75.00%> (-0.05%)	⬇️
unittestcli	55.70% <85.00%> (+0.01%)	⬆️

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[Snuffleupagus]

/botio browsertest

[moz-tools-bot]

From: Bot.io (Linux m4)

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Received

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

Live output at: http://54.241.84.105:8877/0446ed0fb1f2412/output.txt

[moz-tools-bot]

From: Bot.io (Windows)

---

Received

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

Live output at: http://54.193.163.58:8877/120a137b60844aa/output.txt

[moz-tools-bot]

From: Bot.io (Linux m4)

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Failed

Full output at http://54.241.84.105:8877/0446ed0fb1f2412/output.txt

Total script time: 18.10 mins

• Regression tests: FAILED

  different ref/snapshot: 1

Image differences available at: http://54.241.84.105:8877/0446ed0fb1f2412/reftest-analyzer.html#web=eq.log

[moz-tools-bot]

From: Bot.io (Windows)

---

Failed

Full output at http://54.193.163.58:8877/120a137b60844aa/output.txt

Total script time: 24.44 mins

• Regression tests: FAILED

  different ref/snapshot: 1

Image differences available at: http://54.193.163.58:8877/120a137b60844aa/reftest-analyzer.html#web=eq.log

[calixteman]

LGTM. Thank you.