How to programmatically enable flash in Chrome?

Question

Now that flash disabled by default in Chrome 75 our clients is having problems viewing our legacy content which was created using flash. I have referred to this SO question which had a couple of useful answers but for ease-of-use purposes, I'm leaning towards creating an extension that enables flash when a certain URL is accessed.

Chrome extension to enable flash plugin

manifest.json

{
"name": "Flash Enabler",
"version": "1.0",
"description": "Enable flash for Chrome",
"permissions": [
    "contentSettings"
],
"content_scripts": [
    {
        "matches": [
            "https://qa3.icomproductions.ca/*"
        ],
        "js": [
            "content_script.js"
        ]
    }
],
"page_action": {
    "default_icon": {
        "16": "images/ice16.png",
        "32": "images/ice32.png",
        "48": "images/ice48.png",
        "128": "images/ice128.png"
    }
},
"icons": {
    "16": "images/ice16.png",
    "32": "images/ice32.png",
    "48": "images/ice48.png",
    "128": "images/ice128.png"
},
"manifest_version": 2
}

Here's a code based on that OP's snippet:

content_script.js

let flashIdentifier;

chrome.contentSettings.plugins.getResourceIdentifiers(indentifierArray => {
    indentifierArray.forEach(indentifier => {
        indentifier.id === 'adobe-flash-player' ? flashIdentifier = indentifierArray : flashIdentifier = null;
    });

});

chrome.contentSettings.plugins.set({ 'primaryPattern': 'https://qa3.icomproductions.ca/*', 'resourceIdentifier': flashIdentifier, 'setting': 'allow' });
console.log(flashIdentifier);

This generates an error saying:

Any help would be appreciated!