Tests trace events for soft navigations.

PerformanceObserver supports "soft-navigation": true
Recording started

Waited for LCP element with id=click-target

Got soft navigation performance entry: http://127.0.0.1:8000/greeting
Got soft LCP element: Hello, world.

Stopping tracing and analyzing events.
Tracing complete
-> LCP candidate event
   ts: 1
   frame: id_0
   performanceTimelineNavigationId: id_1
-> SoftNavigationStart event
   ts: 2
   frame: id_0
   performanceTimelineNavigationId: id_2
   URL: http://127.0.0.1:8000/greeting
-> SoftNavigationEmitted event
   ts: 3
   performanceTimelineNavigationId: id_2
-> LCP candidate for soft navigation event
   ts: 4
   frame: id_0
   performanceTimelineNavigationId: id_2

SoftNavigationStart event shape:
Object: {
	args: {
		context: {
			URL: string
			domModifications: number
			firstContentfulPaint: number
			paintedArea: number
			performanceTimelineNavigationId: number
			processingEnd: number
			softNavContextId: number
			timeOrigin: number
			urlChangeTime: number
		}
		frame: string
	}
	cat: string
	id2: {
		local: string
	}
	name: string
	ph: string
	pid: number
	tid: number
	ts: number
}

SoftNavigationEmitted event shape:
Object: {
	args: {
		context: {
			URL: string
			domModifications: number
			firstContentfulPaint: number
			paintedArea: number
			performanceTimelineNavigationId: number
			processingEnd: number
			softNavContextId: number
			timeOrigin: number
			urlChangeTime: number
		}
	}
	cat: string
	id2: {
		local: string
	}
	name: string
	ph: string
	pid: number
	tid: number
	ts: number
}

LCP candidate event shape:
Object: {
	args: {
		data: {
			candidateIndex: number
			isMainFrame: boolean
			isOutermostMainFrame: boolean
			navigationId: string
			nodeId: number
			nodeName: string
			performanceTimelineNavigationId: number
			size: number
			type: string
		}
		frame: string
	}
	cat: string
	name: string
	ph: string
	pid: number
	s: string
	tid: number
	ts: number
}

LCP candidate for soft navigation event shape:
Object: {
	args: {
		data: {
			candidateIndex: number
			isMainFrame: boolean
			isOutermostMainFrame: boolean
			nodeId: number
			nodeName: string
			performanceTimelineNavigationId: number
			size: number
			type: string
		}
		frame: string
	}
	cat: string
	name: string
	ph: string
	pid: number
	s: string
	tid: number
	ts: number
}