Fix "inspect" function deprecation notice

Fixes #1326

CHANGELOG.md

@@ -11,6 +11,7 @@ project adheres to [Semantic Versioning](http://semver.org/).
 ### Added
 ### Fixed
 * PDF metadata (added in 2.3.0) wasn't being set with `canvas.createPDFStream()`
+* Fix custom "inspect" function deprecation warnings (#1326)
 
 2.3.1
 ==================

lib/DOMMatrix.js

@@ -1,5 +1,7 @@
 'use strict'
 
+const util = require('util')
+
 // DOMMatrix per https://drafts.fxtf.org/geometry/#DOMMatrix
 
 function DOMPoint(x, y, z, w) {
@@ -127,7 +129,8 @@ DOMMatrix.fromFloat64Array = function (init) {
   return new DOMMatrix(init)
 }
 
-DOMMatrix.prototype.inspect = function (depth, options) {
+// TODO || is for Node.js pre-v6.6.0
+DOMMatrix.prototype[util.inspect.custom || 'inspect'] = function (depth, options) {
   if (depth < 0) return '[DOMMatrix]'
 
   return `DOMMatrix [

lib/canvas.js

@@ -17,17 +17,12 @@ const PNGStream = require('./pngstream')
 const PDFStream = require('./pdfstream')
 const JPEGStream = require('./jpegstream')
 const FORMATS = ['image/png', 'image/jpeg']
+const util = require('util')
 
-/**
- * Inspect canvas.
- *
- * @return {String}
- * @api public
- */
-
-Canvas.prototype.inspect = function(){
-  return '[Canvas ' + this.width + 'x' + this.height + ']';
-};
+// TODO || is for Node.js pre-v6.6.0
+Canvas.prototype[util.inspect.custom || 'inspect'] = function () {
+  return `[Canvas ${this.width}x${this.height}]`
+}
 
 /**
  * Get a context object.

lib/image.js

@@ -14,6 +14,7 @@ const bindings = require('./bindings')
 const Image = module.exports = bindings.Image
 const http = require("http")
 const https = require("https")
+const util = require('util')
 
 const {GetSource, SetSource} = bindings;
 
@@ -72,16 +73,8 @@ Object.defineProperty(Image.prototype, 'src', {
   configurable: true
 });
 
-/**
- * Inspect image.
- *
- * TODO: indicate that the .src was a buffer, data uri etc
- *
- * @return {String}
- * @api public
- */
-
-Image.prototype.inspect = function(){
+// TODO || is for Node.js pre-v6.6.0
+Image.prototype[util.inspect.custom || 'inspect'] = function(){
   return '[Image'
     + (this.complete ? ':' + this.width + 'x' + this.height : '')
     + (this.src ? ' ' + this.src : '')