code: function (benchmark, simultaneousRequests, done) {
  	var pageName,
  		engineName;
  
  	this.benchmark = benchmark;
  	this.simultaneousRequests = simultaneousRequests;
  	this.done = done;
  
  	if (typeof simultaneousRequests !== "number") {
  		throw new Error("simultaneousRequests must be an integer; " + (typeof simultaneousRequests) + " passed");
  	}
  	if (simultaneousRequests < 1) {
  		throw new Error("simultaneousRequests must be at least 1; " + simultaneousRequests + " passed");
  	}
  
  	this.responseTimes = {};
  	for (pageName in this.benchmark.pages) {
  		this.responseTimes[pageName] = {};
  		for (engineName in this.benchmark.engines) {
  			this.responseTimes[pageName][engineName] = [];
  		}
  	}
  
  	this.totals = {};
  }
docs: Instances of BenchmarkContext are one-time only