chore: migrate away from Node's EventEmitter (puppeteer#5979)

docs/api.md

@@ -336,6 +336,15 @@
   * [coverage.stopCSSCoverage()](#coveragestopcsscoverage)
   * [coverage.stopJSCoverage()](#coveragestopjscoverage)
 - [class: TimeoutError](#class-timeouterror)
+- [class: EventEmitter](#class-eventemitter)
+  * [eventEmitter.addListener(event, handler)](#eventemitteraddlistenerevent-handler)
+  * [eventEmitter.emit(event, [eventData])](#eventemitteremitevent-eventdata)
+  * [eventEmitter.listenerCount(event)](#eventemitterlistenercountevent)
+  * [eventEmitter.off(event, handler)](#eventemitteroffevent-handler)
+  * [eventEmitter.on(event, handler)](#eventemitteronevent-handler)
+  * [eventEmitter.once(event, handler)](#eventemitteronceevent-handler)
+  * [eventEmitter.removeAllListeners([event])](#eventemitterremovealllistenersevent)
+  * [eventEmitter.removeListener(event, handler)](#eventemitterremovelistenerevent-handler)
 <!-- GEN:stop -->
 
 ### Overview
@@ -657,7 +666,7 @@ The method initiates a GET request to download the revision from the host.
 
 ### class: Browser
 
-* extends: [EventEmitter](https://nodejs.org/api/events.html#events_class_eventemitter)
+* extends: [EventEmitter](#class-eventemitter)
 
 A Browser is created when Puppeteer connects to a Chromium instance, either through [`puppeteer.launch`](#puppeteerlaunchoptions) or [`puppeteer.connect`](#puppeteerconnectoptions).
 
@@ -819,7 +828,7 @@ You can find the `webSocketDebuggerUrl` from `http://${host}:${port}/json/versio
 
 ### class: BrowserContext
 
-* extends: [EventEmitter](https://nodejs.org/api/events.html#events_class_eventemitter)
+* extends: [EventEmitter](#class-eventemitter)
 
 BrowserContexts provide a way to operate multiple independent browser sessions. When a browser is launched, it has
 a single BrowserContext used by default. The method `browser.newPage()` creates a page in the default browser context.
@@ -949,7 +958,7 @@ const newWindowTarget = await browserContext.waitForTarget(target => target.url(
 
 ### class: Page
 
-* extends: [EventEmitter](https://nodejs.org/api/events.html#events_class_eventemitter)
+* extends: [EventEmitter](#class-eventemitter)
 
 Page provides methods to interact with a single tab or [extension background page](https://developer.chrome.com/extensions/background_pages) in Chromium. One [Browser] instance might have multiple [Page] instances.
 
@@ -966,22 +975,24 @@ const puppeteer = require('puppeteer');
 })();
 ```
 
-The Page class emits various events (described below) which can be handled using any of Node's native [`EventEmitter`](https://nodejs.org/api/events.html#events_class_eventemitter) methods, such as `on`, `once` or `removeListener`.
+The Page class emits various events (described below) which can be handled using
+any of the [`EventEmitter`](#class-eventemitter) methods, such as `on`, `once`
+or `off`.
 
 This example logs a message for a single page `load` event:
 ```js
 page.once('load', () => console.log('Page loaded!'));
 ```
 
-To unsubscribe from events use the `removeListener` method:
+To unsubscribe from events use the `off` method:
 
 ```js
 function logRequest(interceptedRequest) {
   console.log('A request was made:', interceptedRequest.url());
 }
 page.on('request', logRequest);
 // Sometime later...
-page.removeListener('request', logRequest);
+page.off('request', logRequest);
 ```
 
 #### event: 'close'
@@ -3869,7 +3880,7 @@ If the target is not of type `"service_worker"` or `"shared_worker"`, returns `n
 
 ### class: CDPSession
 
-* extends: [EventEmitter](https://nodejs.org/api/events.html#events_class_eventemitter)
+* extends: [EventEmitter](#class-eventemitter)
 
 The `CDPSession` instances are used to talk raw Chrome Devtools Protocol:
 - protocol methods can be called with `session.send` method.
@@ -3975,7 +3986,51 @@ reported.
 
 TimeoutError is emitted whenever certain operations are terminated due to timeout, e.g. [page.waitForSelector(selector[, options])](#pagewaitforselectorselector-options) or [puppeteer.launch([options])](#puppeteerlaunchoptions).
 
+### class: EventEmitter
 
+A small EventEmitter class backed by [Mitt](https://github.com/developit/mitt/).
+
+#### eventEmitter.addListener(event, handler)
+- `event` <[string]|[symbol]> the event to remove the handler from.
+- `handler` <[Function]> the event listener that will be added.
+- returns: `this` so you can chain method calls
+
+This method is identical to `on` and maintained for compatibility with Node's EventEmitter. We recommend using `on` by default.
+
+#### eventEmitter.emit(event, [eventData])
+- `event` <[string]|[symbol]> the event to trigger.
+- `eventData` <[Object]> additional data to send with the event.
+- returns: `boolean`; `true` if there are any listeners for the event, `false` if there are none.
+
+#### eventEmitter.listenerCount(event)
+- `event` <[string]|[symbol]> the event to check for listeners.
+- returns: <[number]> the number of listeners for the given event.
+
+#### eventEmitter.off(event, handler)
+- `event` <[string]|[symbol]> the event to remove the handler from.
+- `handler` <[Function]> the event listener that will be removed.
+- returns: `this` so you can chain method calls
+
+#### eventEmitter.on(event, handler)
+- `event` <[string]|[symbol]> the event to add the handler to.
+- `handler` <[Function]> the event listener that will be added.
+- returns: `this` so you can chain method calls
+
+#### eventEmitter.once(event, handler)
+- `event` <[string]|[symbol]> the event to add the handler to.
+- `handler` <[Function]> the event listener that will be added.
+- returns: `this` so you can chain method calls
+
+#### eventEmitter.removeAllListeners([event])
+- `event` <[string]|[symbol]> optional argument to remove all listeners for the given event. If it's not given this method will remove all listeners for all events.
+- returns: `this` so you can chain method calls
+
+#### eventEmitter.removeListener(event, handler)
+- `event` <[string]|[symbol]> the event to remove the handler from.
+- `handler` <[Function]> the event listener that will be removed.
+- returns: `this` so you can chain method calls
+
+This method is identical to `off` and maintained for compatibility with Node's EventEmitter. We recommend using `off` by default.
 
 [AXNode]: #accessibilitysnapshotoptions "AXNode"
 [Accessibility]: #class-accessibility "Accessibility"
@@ -4024,4 +4079,5 @@ TimeoutError is emitted whenever certain operations are terminated due to timeou
 [selector]: https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Selectors "selector"
 [stream.Readable]: https://nodejs.org/api/stream.html#stream_class_stream_readable "stream.Readable"
 [string]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type "String"
+[symbol]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Symbol_type "Symbol"
 [xpath]: https://developer.mozilla.org/en-US/docs/Web/XPath "xpath"

new-docs/puppeteer.eventemitter.addlistener.md

@@ -0,0 +1,30 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [puppeteer](./puppeteer.md) &gt; [EventEmitter](./puppeteer.eventemitter.md) &gt; [addListener](./puppeteer.eventemitter.addlistener.md)
+
+## EventEmitter.addListener() method
+
+> Warning: This API is now obsolete.
+> 
+> please use `on` instead.
+> 
+
+Add an event listener.
+
+<b>Signature:</b>
+
+```typescript
+addListener(event: EventType, handler: Handler): EventEmitter;
+```
+
+## Parameters
+
+|  Parameter | Type | Description |
+|  --- | --- | --- |
+|  event | EventType |  |
+|  handler | Handler |  |
+
+<b>Returns:</b>
+
+[EventEmitter](./puppeteer.eventemitter.md)
+

new-docs/puppeteer.eventemitter.emit.md

@@ -0,0 +1,27 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [puppeteer](./puppeteer.md) &gt; [EventEmitter](./puppeteer.eventemitter.md) &gt; [emit](./puppeteer.eventemitter.emit.md)
+
+## EventEmitter.emit() method
+
+Emit an event and call any associated listeners.
+
+<b>Signature:</b>
+
+```typescript
+emit(event: EventType, eventData?: any): boolean;
+```
+
+## Parameters
+
+|  Parameter | Type | Description |
+|  --- | --- | --- |
+|  event | EventType | the event you'd like to emit |
+|  eventData | any | any data you'd like to emit with the event |
+
+<b>Returns:</b>
+
+boolean
+
+`true` if there are any listeners, `false` if there are not.
+

new-docs/puppeteer.eventemitter.listenercount.md

@@ -0,0 +1,26 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [puppeteer](./puppeteer.md) &gt; [EventEmitter](./puppeteer.eventemitter.md) &gt; [listenerCount](./puppeteer.eventemitter.listenercount.md)
+
+## EventEmitter.listenerCount() method
+
+Gets the number of listeners for a given event.
+
+<b>Signature:</b>
+
+```typescript
+listenerCount(event: EventType): number;
+```
+
+## Parameters
+
+|  Parameter | Type | Description |
+|  --- | --- | --- |
+|  event | EventType | the event to get the listener count for |
+
+<b>Returns:</b>
+
+number
+
+the number of listeners bound to the given event
+

new-docs/puppeteer.eventemitter.md

@@ -0,0 +1,33 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [puppeteer](./puppeteer.md) &gt; [EventEmitter](./puppeteer.eventemitter.md)
+
+## EventEmitter class
+
+The EventEmitter class that many Puppeteer classes extend.
+
+<b>Signature:</b>
+
+```typescript
+export declare class EventEmitter implements CommonEventEmitter 
+```
+
+## Remarks
+
+This allows you to listen to events that Puppeteer classes fire and act accordingly. Therefore you'll mostly use [on](./puppeteer.eventemitter.on.md) and [off](./puppeteer.eventemitter.off.md) to bind and unbind to event listeners.
+
+The constructor for this class is marked as internal. Third-party code should not call the constructor directly or create subclasses that extend the `EventEmitter` class.
+
+## Methods
+
+|  Method | Modifiers | Description |
+|  --- | --- | --- |
+|  [addListener(event, handler)](./puppeteer.eventemitter.addlistener.md) |  | Add an event listener. |
+|  [emit(event, eventData)](./puppeteer.eventemitter.emit.md) |  | Emit an event and call any associated listeners. |
+|  [listenerCount(event)](./puppeteer.eventemitter.listenercount.md) |  | Gets the number of listeners for a given event. |
+|  [off(event, handler)](./puppeteer.eventemitter.off.md) |  | Remove an event listener from firing. |
+|  [on(event, handler)](./puppeteer.eventemitter.on.md) |  | Bind an event listener to fire when an event occurs. |
+|  [once(event, handler)](./puppeteer.eventemitter.once.md) |  | Like <code>on</code> but the listener will only be fired once and then it will be removed. |
+|  [removeAllListeners(event)](./puppeteer.eventemitter.removealllisteners.md) |  | Removes all listeners. If given an event argument, it will remove only listeners for that event. |
+|  [removeListener(event, handler)](./puppeteer.eventemitter.removelistener.md) |  | Remove an event listener. |
+

new-docs/puppeteer.eventemitter.off.md

@@ -0,0 +1,27 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [puppeteer](./puppeteer.md) &gt; [EventEmitter](./puppeteer.eventemitter.md) &gt; [off](./puppeteer.eventemitter.off.md)
+
+## EventEmitter.off() method
+
+Remove an event listener from firing.
+
+<b>Signature:</b>
+
+```typescript
+off(event: EventType, handler: Handler): EventEmitter;
+```
+
+## Parameters
+
+|  Parameter | Type | Description |
+|  --- | --- | --- |
+|  event | EventType | the event type you'd like to stop listening to. |
+|  handler | Handler | the function that should be removed. |
+
+<b>Returns:</b>
+
+[EventEmitter](./puppeteer.eventemitter.md)
+
+`this` to enable you to chain calls.
+

new-docs/puppeteer.eventemitter.on.md

@@ -0,0 +1,27 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [puppeteer](./puppeteer.md) &gt; [EventEmitter](./puppeteer.eventemitter.md) &gt; [on](./puppeteer.eventemitter.on.md)
+
+## EventEmitter.on() method
+
+Bind an event listener to fire when an event occurs.
+
+<b>Signature:</b>
+
+```typescript
+on(event: EventType, handler: Handler): EventEmitter;
+```
+
+## Parameters
+
+|  Parameter | Type | Description |
+|  --- | --- | --- |
+|  event | EventType | the event type you'd like to listen to. Can be a string or symbol. |
+|  handler | Handler | the function to be called when the event occurs. |
+
+<b>Returns:</b>
+
+[EventEmitter](./puppeteer.eventemitter.md)
+
+`this` to enable you to chain calls.
+

new-docs/puppeteer.eventemitter.once.md

@@ -0,0 +1,27 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [puppeteer](./puppeteer.md) &gt; [EventEmitter](./puppeteer.eventemitter.md) &gt; [once](./puppeteer.eventemitter.once.md)
+
+## EventEmitter.once() method
+
+Like `on` but the listener will only be fired once and then it will be removed.
+
+<b>Signature:</b>
+
+```typescript
+once(event: EventType, handler: Handler): EventEmitter;
+```
+
+## Parameters
+
+|  Parameter | Type | Description |
+|  --- | --- | --- |
+|  event | EventType | the event you'd like to listen to |
+|  handler | Handler | the handler function to run when the event occurs |
+
+<b>Returns:</b>
+
+[EventEmitter](./puppeteer.eventemitter.md)
+
+`this` to enable you to chain calls.
+

new-docs/puppeteer.eventemitter.removealllisteners.md

@@ -0,0 +1,26 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [puppeteer](./puppeteer.md) &gt; [EventEmitter](./puppeteer.eventemitter.md) &gt; [removeAllListeners](./puppeteer.eventemitter.removealllisteners.md)
+
+## EventEmitter.removeAllListeners() method
+
+Removes all listeners. If given an event argument, it will remove only listeners for that event.
+
+<b>Signature:</b>
+
+```typescript
+removeAllListeners(event?: EventType): EventEmitter;
+```
+
+## Parameters
+
+|  Parameter | Type | Description |
+|  --- | --- | --- |
+|  event | EventType | the event to remove listeners for. |
+
+<b>Returns:</b>
+
+[EventEmitter](./puppeteer.eventemitter.md)
+
+`this` to enable you to chain calls.
+

new-docs/puppeteer.eventemitter.removelistener.md

@@ -0,0 +1,30 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [puppeteer](./puppeteer.md) &gt; [EventEmitter](./puppeteer.eventemitter.md) &gt; [removeListener](./puppeteer.eventemitter.removelistener.md)
+
+## EventEmitter.removeListener() method
+
+> Warning: This API is now obsolete.
+> 
+> please use `off` instead.
+> 
+
+Remove an event listener.
+
+<b>Signature:</b>
+
+```typescript
+removeListener(event: EventType, handler: Handler): EventEmitter;
+```
+
+## Parameters
+
+|  Parameter | Type | Description |
+|  --- | --- | --- |
+|  event | EventType |  |
+|  handler | Handler |  |
+
+<b>Returns:</b>
+
+[EventEmitter](./puppeteer.eventemitter.md)
+