mre: chrome may not gc filereader output used by wasm inside webworkers

select a file which exceeds 24 MiB in size: 
screenshot latest official gchrome beta on win10-ltsc

hashing speed: --- MiB/s

reliably observed on:
* win10-1809 (17763.316)  + chr 105.0.5195.37 (latest official gchrome beta)
* win10-1809 (17763.3046) + chr 106.0.5229.0 (#1032995, gc@appspot)

NOT observed with THIS mre, however reliably OBSERVED in the full application:
* win10-1809 (17763.3046) + chr  90.0.4416.0 (#853132, gc@appspot)
* win10-1809 (17763.3046) + chr  97.0.4689.0 (#937004, gc@appspot)

NOT observed with THIS mre, however reliably OBSERVED in the full application
unless the equivalence of `apply_workaround = true` is inserted into `w.hash.js`:
* win10-1809 (17763.3046) + chr  93.0.4531.0 (#888620, gc@appspot)
* win10-1809 (17763.3046) + chr  93.0.4552.0 (#895174, gc@appspot)
* win10-1809 (17763.3046) + chr  97.0.4666.0 (#929984, gc@appspot)
* win10-1809 (17763.3046) + chr 105.0.5164.0 (#1021082, gc@appspot)
* win10-1809 (17763.3046) + chr 106.0.5247.0 (#1036146, gc@appspot)

NOT observed on:
* win10-1809 (17763.316)  + chr 104.0.5112.102 (latest official gchrome stable)
* win10-1809 (17763.3046) + chr  84.0.4115.0 (#758826, gc@appspot)
* win10-1809 (17763.3046) + chr  88.0.4322.0 (#825998, gc@appspot)
* win10-1809 (17763.3046) + chr  95.0.4631.0 (#917620, gc@appspot)
* win10-1809 (17763.3046) + chr  98.0.4719.0 (#943825, gc@appspot)
* win10-1809 (17763.3046) + chr  98.0.4732.0 (#945698, gc@appspot)
* win10-1809 (17763.3046) + chr 102.0.4991.0 (#990124, gc@appspot)
* win10-1809 (17763.3046) + chr 106.0.5247.0 (#1036146, gc@appspot)

(17763.316 = stock LTSC-2019 without any updates)

--

for any brave souls who wish to try the full application:
download the python file linked below, run it with arguments `-nw -e2d`,
access it over plaintext http *from another machine*
(so that crypto.subtle is disabled and it uses the wasm fallback),
and dragdrop a file larger than 4 GiB into your browser

* dragdrop onto "search" is enough to repro the bug
* dragdrop onto "upload" also fine; `-nw` disables writing to disk
* files that are exactly 4 GiB or smaller will NOT repro; need 0x100000001 bytes
* https:// instead of http:// will disable wasm and NOT repro
  * it should show a "you should switch to https" banner while hashing

https://github.com/9001/copyparty/releases/download/v1.3.15/copyparty-sfx.py

(v1.3.16 and later have the `apply_workaround` fix but disables webworkers
  in chrome by default; go to ⚙️settings and enable "mt" to repro the bug)