feat: add enableLocalEcho flag to setDisplayMediaRequestHandler() callback (#37315)

docs/api/session.md

@@ -916,6 +916,10 @@ session.fromPartition('some-partition').setPermissionCheckHandler((webContents,
         Specifying a loopback device will capture system audio, and is
         currently only supported on Windows. If a WebFrameMain is specified,
         will capture audio from that frame.
+      * `enableLocalEcho` Boolean (optional) - If `audio` is a [WebFrameMain](web-frame-main.md)
+         and this is set to `true`, then local playback of audio will not be muted (e.g. using `MediaRecorder`
+         to record `WebFrameMain` with this flag set to `true` will allow audio to pass through to the speakers
+         while recording). Default is `false`.
 
 This handler will be called when web content requests access to display media
 via the `navigator.mediaDevices.getDisplayMedia` API. Use the

shell/browser/electron_browser_context.cc

@@ -501,13 +501,16 @@ void ElectronBrowserContext::DisplayMediaDeviceChosen(
       devices.audio_device =
           blink::MediaStreamDevice(request.audio_type, id, name);
     } else if (result_dict.Get("audio", &rfh)) {
-      devices.audio_device = blink::MediaStreamDevice(
-          request.audio_type,
-          content::WebContentsMediaCaptureId(rfh->GetProcess()->GetID(),
-                                             rfh->GetRoutingID(),
-                                             /* disable_local_echo= */ true)
-              .ToString(),
-          "Tab audio");
+      bool enable_local_echo = false;
+      result_dict.Get("enableLocalEcho", &enable_local_echo);
+      bool disable_local_echo = !enable_local_echo;
+      devices.audio_device =
+          blink::MediaStreamDevice(request.audio_type,
+                                   content::WebContentsMediaCaptureId(
+                                       rfh->GetProcess()->GetID(),
+                                       rfh->GetRoutingID(), disable_local_echo)
+                                       .ToString(),
+                                   "Tab audio");
     } else if (result_dict.Get("audio", &id)) {
       devices.audio_device =
           blink::MediaStreamDevice(request.audio_type, id, "System audio");