Expose HitCount and HitLineCount to CPUProfileNode

[mnutt]

This exposes hitCount and hitLineCount from v8's cpuprofile node. It's useful in order to be able to see relative percentages of time spent in a v8 function and its descendants, although computing total time is left up to the presentation implementation.

Sample implementation:

func printTree(nest string, node *v8.CPUProfileNode) {
	file, name, line, col := node.GetScriptResourceName(), node.GetFunctionName(), node.GetLineNumber(), node.GetColumnNumber()
	selfHits, totalHits := node.GetHitCount(), totalHitCountForNode(node)

	fmt.Printf("[%d/%d hits\t]  %s%s() %s:%d:%d\n", selfHits, totalHits, nest, name, file, line, col)

	count := node.GetChildrenCount()
	if count == 0 {
		return
	}

	nest = fmt.Sprintf("%s  ", nest)

	for i := 0; i < count; i++ {
		printTree(nest, node.GetChild(i))
	}
}

func totalHitCountForNode(node *v8.CPUProfileNode) uint {
	totalHitCount := node.GetHitCount()

	count := node.GetChildrenCount()
	for i := 0; i < count; i++ {
		totalHitCount += totalHitCountForNode(node.GetChild(i))
	}

	return totalHitCount
}

[genevieve]

Would you be open to using the comment from the v8 header file for these?

i.e.

// The count of samples where the function was currently executing.
hitCount uint

// The number of the function's source lines that collect the samples.
hitLineCount uint

[genevieve]

Same for the getters ^

[genevieve]

The changes look good.

1. Could you update the changelog to reflect these two new functions on nodes?
2. Are there test assertions in the node suite that could cover these two new functions while also being reliable?

[codecov]

Codecov Report

Merging #285 (99bdd18) into master (5e91d3d) will decrease coverage by 0.31%.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##           master     #285      +/-   ##
==========================================
- Coverage   95.86%   95.54%   -0.32%     
==========================================
  Files          17       17              
  Lines         580      584       +4     
==========================================
+ Hits          556      558       +2     
- Misses         15       17       +2     
  Partials        9        9              

Impacted Files	Coverage Δ
cpuprofilenode.go	77.77% <0.00%> (-22.23%)	⬇️
cpuprofiler.go	100.00% <100.00%> (ø)

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