Bugzilla

FWIW, what's causing silent printing to fail in the first place is that part 3 of bug 1669149 meant silent printing no longer enters the [section of nsPrintJob::DoCommonPrint that does the event loop spinning to "open" a system print dialog in the parent process](https://searchfox.org/mozilla-central/rev/e74a8e2d1dedebfe47a6afb009ddabdeea12694b/layout/printing/nsPrintJob.cpp#643-644,672-673) to get the print settings to use. That causes us to error out [later in nsPrintJob::DoCommonPrint](https://searchfox.org/mozilla-central/rev/e74a8e2d1dedebfe47a6afb009ddabdeea12694b/layout/printing/nsPrintJob.cpp#749-750) when we call nsDeviceContextSpecProxy::Init. That's because [nsDeviceContextSpecProxy::Init fails if we don't have a RemotePrintJobChild](https://searchfox.org/mozilla-central/rev/e74a8e2d1dedebfe47a6afb009ddabdeea12694b/widget/nsDeviceContextSpecProxy.cpp#64-67), which is what the call to "open" the print dialog in the parent process got us.

FWIW, what's causing silent printing to fail in the first place is that part 3 of bug 1669149 meant silent printing no longer enters the [section of nsPrintJob::DoCommonPrint that does the event loop spinning to "open" a system print dialog in the parent process](https://searchfox.org/mozilla-central/rev/e74a8e2d1dedebfe47a6afb009ddabdeea12694b/layout/printing/nsPrintJob.cpp#643-644,672-673) to get the print settings that should be used. That causes us to error out [later in nsPrintJob::DoCommonPrint](https://searchfox.org/mozilla-central/rev/e74a8e2d1dedebfe47a6afb009ddabdeea12694b/layout/printing/nsPrintJob.cpp#749-750) when we call nsDeviceContextSpecProxy::Init. That's because [nsDeviceContextSpecProxy::Init fails if we don't have a RemotePrintJobChild](https://searchfox.org/mozilla-central/rev/e74a8e2d1dedebfe47a6afb009ddabdeea12694b/widget/nsDeviceContextSpecProxy.cpp#64-67), which is what the call to "open" the print dialog in the parent process got us.