Added support for a desynchronized context and alpha support in 2D

Author: photonstorm

src/core/Config.js

@@ -337,6 +337,11 @@ var Config = new Class({
          */
         this.antialias = GetValue(renderConfig, 'antialias', true);
 
+        /**
+         * @const {boolean} Phaser.Core.Config#desynchronized - When set to `true` it will create a desynchronized context for both 2D and WebGL. See https://developers.google.com/web/updates/2019/05/desynchronized for details.
+         */
+        this.desynchronized = GetValue(renderConfig, 'desynchronized', false);
+
         /**
          * @const {boolean} Phaser.Core.Config#roundPixels - Draw texture-based Game Objects at only whole-integer positions. Game Objects without textures, like Graphics, ignore this property.
          */

src/core/typedefs/RenderConfig.js

@@ -110,14 +110,19 @@ var CanvasRenderer = new Class({
          */
         this.gameCanvas = game.canvas;
 
+        var contextOptions = {
+            alpha: game.config.transparent,
+            desynchronized: game.config.desynchronized
+        };
+
         /**
          * The canvas context used to render all Cameras in all Scenes during the game loop.
          *
          * @name Phaser.Renderer.Canvas.CanvasRenderer#gameContext
          * @type {CanvasRenderingContext2D}
          * @since 3.0.0
          */
-        this.gameContext = (this.game.config.context) ? this.game.config.context : this.gameCanvas.getContext('2d');
+        this.gameContext = (this.game.config.context) ? this.game.config.context : this.gameCanvas.getContext('2d', contextOptions);
 
         /**
          * The canvas context currently used by the CanvasRenderer for all rendering operations.

src/renderer/canvas/CanvasRenderer.js

@@ -57,6 +57,7 @@ var WebGLRenderer = new Class({
 
         var contextCreationConfig = {
             alpha: gameConfig.transparent,
+            desynchronized: gameConfig.desynchronized,
             depth: false,
             antialias: gameConfig.antialias,
             premultipliedAlpha: gameConfig.premultipliedAlpha,