Use pprof web interface

[firelizzard18]

From a conversation on CL 344149

@hyangah

I wondered if it's possible to borrow the pprof's web interface (available through -http=localhost:12345). But that will require to run a pprof server. (user clicks a "open pprof UI" button, that triggers pprof -http=:port ... and let the default browser open (which pprof handles)?

@firelizzard18

I think we can probably do that. Run the server and then launch a webview. It might require an iframe, but VSCode might explicitly block browsing to random webpages. I'll look into it. I'd rather do that as a separate CL, to keep this one small.

[firelizzard18]

I still need to check if this is an option (if VSCode allows webviews to point at localhost:12345)

[firelizzard18]

@hyangah I have verified that this can be done with an <iframe>. It's essentially identical to visualizing via pprof -dot, except the process continues running and the webview HTML embeds an iframe instead of an SVG.

[firelizzard18]

Here's what it looks like in an iframe:

[gopherbot]

Change https://golang.org/cl/345477 mentions this issue: src/goTest: visualize profiles