Add memory heap snapshot API

[robrbecker]

Problem

I see there is an API for starting and stoping a timeline recording await page.tracing.start({path: 'trace.json'}); but I would like to request the ability to take a memory heap snapshot and the ability to write expectations on the snapshot data.

My use case is roughly:

• load a page
• load a component & do stuff
• remove the component
• force a garbage collection (would love a method for this as well!)
• take a heap snapshot
• Verify that the component is not retained in memory somehow

This would be amazing to be able to have automated headless memory leak regression testing!

Maybe something like:

var heapsnap = await page.heap.snapshot('heap1.snapshot');
expect(!heapsnap.contains('SomeClassName'))

Bonus points for an API for the memory allocation timeline that you could query for the number of objects of a type added / removed during the timeline.

[aslushnikov]

@ak239 is claiming this!

[robbecker-wf]

[NicolasRannou]

Amazing - any snippet available to get quickly started on memory leak testing? So amazing I've been waiting for that for years!

[aslushnikov]

@NicolasRannou we have a small demo in the api docs: page.queryObjects

[NicolasRannou]

Thanks a lot I missed that!

[georgelesica-wf]

I don't quite see how the referenced PR really resolved this issue. In order for the page.queryObjects method to be useful it seems I still need to know what I'm looking for. What I think this issue was asking for is an API to allow aggregation and possibly logging of all objects currently allocated, probably with metadata (prototype, and so on). Am I wrong?