KeyStroke Input not working in Chrome

Question

I am trying to send keystroke inputs using a Chrome Extension on React sites and unable to get it to work. Here is a snippet of code to type 'a' on google.com

I have based this on the answer for Firing a keyboard event on Chrome and it doesnt work.

function createKeyboardEvent (aType, aTarget, aKeyCode, opt_keyModifiers) {
    var mods, match, domEvent;
    mods = (opt_keyModifiers == null) ? '' : opt_keyModifiers;
    match = /\[(.*)\]/.exec(aKeyCode);
    var keyCode, charCode, which;

    var key = String.fromCharCode(aKeyCode).toLowerCase();
    keyCode = aKeyCode;
    which = aKeyCode;
    charCode = 0;

    domEvent = new window.KeyboardEvent(aType, {
       bubbles: true,
       cancelable: true,
       ctrlKey: mods.indexOf('ctrlKey') !== -1,
       altKey: mods.indexOf('altKey') !== -1,
       shiftKey: mods.indexOf('shiftKey') !== -1,
       metaKey: mods.indexOf('metaKey') !== -1,
       key: key,
       charCode: 0,
       which: keyCode,
       keyCode: keyCode,
       codeVal: "KeyA",
       view: window
    });

    // Chromium Hack. With Chrome 43, our setting of keycode and
    // charcode was deprecated.
    Object.defineProperty(domEvent, 'keyCode', {
        get : function() {
            return this.keyCodeVal;
        }
    });     
    Object.defineProperty(domEvent, 'which', {
        get : function() {
            return this.whichVal;
        }
    });           
    Object.defineProperty(domEvent, 'charCode', {
        get : function() {
            return this.charCodeVal;
        }
    });
    Object.defineProperty(domEvent, 'key', {
        get : function() {
            return this.keyVal;
        }
    });
    Object.defineProperty(domEvent, 'code', {
        get : function() {
            return this.codeVal;
        }
    });
    domEvent.charCodeVal = charCode;
    domEvent.keyCodeVal = keyCode;
    domEvent.whichVal = which;
    domEvent.keyVal = key;
    domEvent.codeVal = "KeyA";
    aTarget.dispatchEvent(domEvent);
}

// Type 'a'
var target = document.getElementById('lst-ib');
target.focus();
var nextKeyCode = 65;
createKeyboardEvent('keydown', target, nextKeyCode);
createKeyboardEvent('keypress', target, nextKeyCode);
createKeyboardEvent('keyup', target, nextKeyCode);