Bugzilla

I suspect this is taking so long due to the fact that the *reference case* is loading so many `embed` elements -- 144 of them, to be exact -- and there's probably some overhead associated with doing that.  I do see them appearing to load a bit slowly/incrementally in my local debug build, at least.

Also, it looks like this slowness isn't entirely Android-specific - here are some logs where this test takes between 4s-16s on linux debug, TSAN, and ASAN (whereas the previous test takes 200-500ms):
tsan: https://treeherder.mozilla.org/logviewer?job_id=504037856&repo=autoland&lineNumber=8757
asan: https://treeherder.mozilla.org/logviewer?job_id=504043567&repo=autoland&lineNumber=22373
debug: https://treeherder.mozilla.org/logviewer?job_id=504035101&repo=autoland&lineNumber=26421

I took a performance profile in my local debug build, and it looks like most of the time is spent setting up the embedded document, its JS global 'window' object, and stuff like that (for all of the 144 documents).  That overhead is all not really necessary/interesting, so I'm going to simplify the testcase to just use specially crafted `divs` to mock up the expected rendering.  That version loads ~instantly.

I suspect this is taking so long due to the fact that the *reference case* is loading so many `embed` elements -- 144 of them, to be exact -- and there's probably some overhead associated with doing that.  I do see them appearing to load a bit slowly/incrementally in my local debug build, at least.

Also, it looks like this slowness isn't entirely Android-specific - here are some logs where this test takes between 4s-16s on linux debug, TSAN, and ASAN (whereas the previous test takes 200-500ms):
tsan: https://treeherder.mozilla.org/logviewer?job_id=504037856&repo=autoland&lineNumber=8757
asan: https://treeherder.mozilla.org/logviewer?job_id=504043567&repo=autoland&lineNumber=22373
debug: https://treeherder.mozilla.org/logviewer?job_id=504035101&repo=autoland&lineNumber=26421

I took a performance profile in my local debug build, and it looks like most of the time is spent setting up the embedded document, its JS global 'window' object, and stuff like that (for all of the 144 documents).  That overhead is all not really necessary/interesting (and is a waste of compute time on our test runners - this test isn't worth burning 10-20 seconds on for each test run); so I'm going to simplify the testcase to just use specially crafted `divs` to mock up the expected rendering.  That version loads ~instantly.