perf: use Date.now() instead of new Date().getTime()

new Date().getTime() is 2x slower than Date.now(), see https://jsperf.com/new-date-vs-date-now-vs-performance-now/6

lib/Compiler.js

@@ -36,7 +36,7 @@ function Watching(compiler, watchOptions, handler) {
 
 Watching.prototype._go = function() {
 	var self = this;
-	self.startTime = new Date().getTime();
+	self.startTime = Date.now();
 	self.running = true;
 	self.invalid = false;
 	self.compiler.applyPluginsAsync("watch-run", self, function(err) {
@@ -61,7 +61,7 @@ Watching.prototype._go = function() {
 
 						var stats = new Stats(compilation);
 						stats.startTime = self.startTime;
-						stats.endTime = new Date().getTime();
+						stats.endTime = Date.now();
 						self.compiler.applyPlugins("done", stats);
 
 						self.compiler.applyPluginsAsync("additional-pass", function(err) {
@@ -80,7 +80,7 @@ Watching.prototype._go = function() {
 Watching.prototype._getStats = function(compilation) {
 	var stats = new Stats(compilation);
 	stats.startTime = this.startTime;
-	stats.endTime = new Date().getTime();
+	stats.endTime = Date.now();
 	return stats;
 };
 
@@ -222,7 +222,7 @@ Compiler.prototype.watch = function(watchOptions, handler) {
 
 Compiler.prototype.run = function(callback) {
 	var self = this;
-	var startTime = new Date().getTime();
+	var startTime = Date.now();
 
 	self.applyPluginsAsync("before-run", self, function(err) {
 		if(err) return callback(err);
@@ -239,7 +239,7 @@ Compiler.prototype.run = function(callback) {
 					if(self.applyPluginsBailResult("should-emit", compilation) === false) {
 						var stats = new Stats(compilation);
 						stats.startTime = startTime;
-						stats.endTime = new Date().getTime();
+						stats.endTime = Date.now();
 						self.applyPlugins("done", stats);
 						return callback(null, stats);
 					}
@@ -252,7 +252,7 @@ Compiler.prototype.run = function(callback) {
 
 							var stats = new Stats(compilation);
 							stats.startTime = startTime;
-							stats.endTime = new Date().getTime();
+							stats.endTime = Date.now();
 							self.applyPlugins("done", stats);
 
 							self.applyPluginsAsync("additional-pass", function(err) {
@@ -267,7 +267,7 @@ Compiler.prototype.run = function(callback) {
 
 							var stats = new Stats(compilation);
 							stats.startTime = startTime;
-							stats.endTime = new Date().getTime();
+							stats.endTime = Date.now();
 							self.applyPlugins("done", stats);
 							return callback(null, stats);
 						});

lib/ContextModule.js

@@ -99,7 +99,7 @@ class ContextModule extends Module {
 
 	build(options, compilation, resolver, fs, callback) {
 		this.built = true;
-		this.builtTime = new Date().getTime();
+		this.builtTime = Date.now();
 		this.resolveDependencies(fs, this.context, this.recursive, this.regExp, (err, dependencies) => {
 			if(err) return callback(err);
 

lib/DelegatedModule.js

@@ -37,7 +37,7 @@ class DelegatedModule extends Module {
 
 	build(options, compilation, resolver, fs, callback) {
 		this.built = true;
-		this.builtTime = new Date().getTime();
+		this.builtTime = Date.now();
 		this.usedExports = true;
 		this.providedExports = this.delegateData.exports || true;
 		this.dependencies.length = 0;

lib/ExternalModule.js

@@ -35,7 +35,7 @@ class ExternalModule extends Module {
 	}
 
 	build(options, compilation, resolver, fs, callback) {
-		this.builtTime = new Date().getTime();
+		this.builtTime = Date.now();
 		callback();
 	}
 

lib/NormalModule.js

@@ -257,7 +257,7 @@ class NormalModule extends Module {
 	}
 
 	build(options, compilation, resolver, fs, callback) {
-		this.buildTimestamp = new Date().getTime();
+		this.buildTimestamp = Date.now();
 		this.built = true;
 		this._source = null;
 		this.error = null;

lib/RawModule.js

@@ -36,7 +36,7 @@ module.exports = class RawModule extends Module {
 	}
 
 	build(options, compilations, resolver, fs, callback) {
-		this.builtTime = new Date().getTime();
+		this.builtTime = Date.now();
 		callback();
 	}