fix: crash on printer dialog cancellation

[codebytere]

Description of Change

Closes #32684.

This PR fixes a crash that occurred when a user attempted to print a document either with window.print(), the print button in the PDF viewer, or with BrowserWindow.webContents() and clicked cancel in the resulting print dialog. This was introduced in e693ad9 as a result of an attempt to handle upstream changed in CL:3305095. This added a new function OnUserInitCancelled to the PrintJob Observer with the intent that when a job was cancelled it would broadcast to an observed function OnUserInitCancelled() in PrintViewManagerBase. However, there is one critical problem with that - that print_job_ does not exist that that point and is intialized afterwards here. As such, print_job->OnUserInitCancelled() was a null pointer crash. We fix this by moving the cancellation check to ScriptedPrintReplyOnIO.

Checklist

• PR description included and stakeholders cc'd
• npm test passes
• PR release notes describe the change in a way relevant to app developers, and are capitalized, punctuated, and past tense.

Release Notes

Notes: Fixed a crash that occurred when a user attempted to print a document either with window.print(), the print button in the PDF viewer, or with BrowserWindow.webContents() and clicked cancel in the resulting print dialog

[VerteDinde]

Thank you! 🙇‍♀️

[deepak1556]

ScriptedPrintReplyOnIO will yield back to UI thread via ScriptedPrintReply , the user cancellation check can be performed there and end up calling UserInitCancelled directly. This will reduce the patch to not pass around the manager class weak ptr to the different sequences and also avoid the necessity to create a separate UI task NotifyUserCancelled

Another question, the scripted print sequences will be triggered for renderer initiated print calls like the pdf viewer print and window.print but will this also handle the case for webContents.print as mentioned in the PR description ?

[codebytere]

@deepak1556 updated and tested with https://gist.github.com/0f0e776b138452d6815ef4efc16aa0d1 to confirm that this fix covers relevant scenarios.

[release-clerk]

Release Notes Persisted

Fixed a crash that occurred when a user attempted to print a document either with window.print(), the print button in the PDF viewer, or with BrowserWindow.webContents() and clicked cancel in the resulting print dialog

[trop]

I was unable to backport this PR to "17-x-y" cleanly;
you will need to perform this backport manually.

[pushkin-]

When can we expect a backport of this (to 17)?

[trop]

@codebytere has manually backported this PR to "17-x-y", please check out #33015