docs: Use app.disableHardwareAcceleration() instead of --disable-gpu

The --disable-gpu switch does not work when passed with `appendSwitch`.

docs/api/chrome-command-line-switches.md

@@ -175,36 +175,6 @@ logging level for all code in the source files under a `foo/bar` directory.
 
 This switch only works when `--enable-logging` is also passed.
 
-## --disable-gpu
-
-Disables the use of the GPU in the renderer process. If this is set with the
-`--disable-gpu-compositing` switch, *offscreen rendering* will use a software
-output device, which has much better overall performance but lacks of WebGL
-and 3D CSS support.
-
-## --disable-gpu-compositing
-
-Disables the use of the GPU compositing in the renderer process. This should be
-set with the `--disable-gpu` switch for *offscreen rendering*.
-
-``` javascript
-const {app, BrowserWindow} = require('electron');
-
-app.commandLine.appendSwitch('disable-gpu');
-app.commandLine.appendSwitch('disable-gpu-compositing');
-
-let win = new BrowserWindow({
-  webPreferences: {
-    offscreen: true
-  }
-});
-win.loadURL('http://github.com');
-
-win.webContents.on('paint', (event, dirty, data) => {
-  updateBitmap(dirty, data);
-});
-```
-
 [app]: app.md
 [append-switch]: app.md#appcommandlineappendswitchswitch-value
 [ready]: app.md#event-ready

docs/tutorial/offscreen-rendering.md

@@ -25,22 +25,17 @@ mode that WebGL and 3D CSS animations are supported.
 
 This mode uses a software output device for rendering in the CPU, so the frame
 generation is much faster, thus this mode is preferred over the GPU accelerated
-one. To enable this mode GPU acceleration has to be disabled like this:
+one.
 
-``` javascript
-const {app} = require('electron')
-
-app.commandLine.appendSwitch('disable-gpu')
-app.commandLine.appendSwitch('disable-gpu-compositing')
-```
+To enable this mode GPU acceleration has to be disabled by calling the
+[`app.disableHardwareAcceleration()`][disablehardwareacceleration] API.
 
 ## Usage
 
 ``` javascript
 const {app, BrowserWindow} = require('electron')
 
-app.commandLine.appendSwitch('disable-gpu')
-app.commandLine.appendSwitch('disable-gpu-compositing')
+app.disableHardwareAcceleration()
 
 let win = new BrowserWindow({
   width: 800,
@@ -57,3 +52,5 @@ win.webContents.on('paint', (event, dirty, data) => {
   // updateBitmap(dirty, data)
 })
 ```
+
+[disablehardwareacceleration]: ../api/app.md#appdisablehardwareacceleration