nsImageGeometryMixin is used to redraw images with sync decoding. Without it,
if we paint an image with non-sync decoding, we won't know that it will be
drawn differently with sync decoding and so don't have a mechanism to include
it in the invalid region.

Currently the main situation where we draw images with non-sync decoding and
then with sync decoding is during reftests. If we unconditionally use sync
decoding during reftests we don't have to worry about the situation where we
switch. This will let us resolve the problems associated with nsImageGeometryMixin.

nsImageGeometryMixin is used to redraw images with sync decoding. Without it,
if we paint an image with non-sync decoding, we won't know that it will be
drawn differently with sync decoding and so don't have a mechanism to include
it in the invalid region.

Currently the main situation where we draw images with non-sync decoding and
then with sync decoding is during reftests. If we unconditionally use sync
decoding during reftests we don't have to worry about the situation where we
switch. This will let us resolve the problems associated with nsImageGeometryMixin.

Backed out for causing crashtest failures on 944353.jpg.

Push with failures

Failure log

Backout link

[task 2022-06-17T19:34:27.391Z] 19:34:27     INFO -  REFTEST TEST-START | image/test/crashtests/944353.jpg
[task 2022-06-17T19:34:27.391Z] 19:34:27     INFO -  REFTEST TEST-LOAD | http://10.0.2.2:8854/tests/image/test/crashtests/944353.jpg | 1382 / 3943 (35%)
[task 2022-06-17T19:40:53.355Z] 19:40:53     INFO -  REFTEST INFO | wait for org.mozilla.geckoview.test_runner complete; top activity=org.mozilla.geckoview.test_runner
[task 2022-06-17T19:40:53.355Z] 19:40:53     INFO -  REFTEST INFO | org.mozilla.geckoview.test_runner unexpectedly found running. Killing...
[task 2022-06-17T19:41:06.672Z] 19:41:06  WARNING -  REFTEST ERROR | TEST-UNEXPECTED-FAIL | image/test/crashtests/944353.jpg | application timed out after 370 seconds with no output
[task 2022-06-17T19:41:06.672Z] 19:41:06     INFO -  REFTEST INFO | remotereftest.py | Application ran for: 0:09:56.962102
[task 2022-06-17T19:41:07.277Z] 19:41:07     INFO -  leakcheck | refcount logging is off, so leaks can't be detected!
[task 2022-06-17T19:41:07.344Z] 19:41:07    ERROR - Return code: 1
[task 2022-06-17T19:41:07.344Z] 19:41:07    ERROR - No tests run or test summary not found
[task 2022-06-17T19:41:07.344Z] 19:41:07     INFO - TinderboxPrint: crashtest<br/><em class="testfail">T-FAIL</em>
[task 2022-06-17T19:41:07.344Z] 19:41:07     INFO - ##### crashtest log ends
[task 2022-06-17T19:41:07.345Z] 19:41:07  WARNING - # TBPL WARNING #
[task 2022-06-17T19:41:07.345Z] 19:41:07  WARNING - setting return code to 1
[task 2022-06-17T19:41:07.345Z] 19:41:07  WARNING - The crashtest suite: crashtest ran with return status: WARNING

This is OOMing. I guess because of the large image?

I'm going to check how far we get into loading the image with sync decoding turned off.

We call AllocateBufferForImage 8268 12402 4 during sync decoding vs 1 during non-sync decoding which I find surprising.

https://hg.mozilla.org/mozilla-central/rev/eae358b04c3a