Odd behaviour with LINE_LOOP in osmesa

[asajeffrey]

With surfman, headless servo fails /_webgl/conformance/rendering/more-than-65536-indices.html due to LINE_LOOP drawing yellow rather than green.:

  FAIL WebGL test #8: Should be green.
at (0, 0) expected: 0,255,0,255 was 128,128,0,255 - assert_true: Should be green.
at (0, 0) expected: 0,255,0,255 was 128,128,0,255 expected true got false

The test passes in x11, and passes if the tests are reordered to make the LINE_LOOP test first. This appears to be an odd feature of osmesa.

[SimonSapin]

OSMesa-src is no longer used since #25853, is this still relevant?

[jdm]

No.