When invoking `./mach cargo` the following error appeared
```
Error running mach:
['cargo']
The error occurred in the implementation of the invoked mach command.
This should never occur and is likely a bug in the implementation of that
command. Consider filing a bug for this issue.
If filing a bug, please include the full output of mach, including this error
message.
The details of the failure are as follows:
TypeError: can only concatenate list (not "NoneType") to list
File "/home/tj/servo/python/servo/devenv_commands.py", line 24, in cargo
return subprocess.call(["cargo"] + params,
```
it seems to be that all that's missing is checking whether params is None or not.
through display list building.
The old `flow_origin` concept was ill-defined (sometimes the border box
plus the flow origin, sometimes including horizontal margins and
sometimes not, sometimes including relative position and sometimes not),
leading to brittleness and test failures. This commit reworks the logic
to always pass border box origins in during display list building.
A lot of tests were failing when I ran `./mach test tests/wpt/web-platform-tests/workers --processes=4` and
`./mach test tests/wpt/web-platform-tests/XMLHttpRequest --processes=4` on master. So I could not completely test it. I verified that the tests that were failing were the same, before and after the change.
Is there any way to run it here?
It is possible for a PaintTask to start exiting soon after sending new
buffers to the compositor. In that case, the compositor should return
the now unnecessary buffers to the PaintTask so that it can properly
free them.
To accomplish this, the compositor now keeps a hash map of paint task
channels per pipeline id. When a PaintTask exists, the constellation
informs the compositor that it can forget about it. Additionally, the
PaintTask should not wait for any buffers when the engine is doing a
complete shutdown. In that case, the compositor is already halted and
has simply let all buffers leak. We pipe through the shutdown type when
destroying the pipeline to make this decision.
Fixes#2641.
