Text in buttons are not centered vertically in Firefox

[ppawlak]

This happens only with Firefox : texts in all buttons of my game are not centered vertically, they are a little bit too high. The bigger the font is, the more they are not centered. This happens only if I set a custom font, whatever the font is.

I made a little code snippet to demonstrate :

    var TestLayer = cc.Layer.extend({

        ctor: function () {
            this._super();

            var button = new ccui.Button();
            button.setTitleText("CLICK");
            button.setTitleFontSize(36);
            button.setTitleFontName("Cocogoose");
            button.loadTextureNormal("res/images/button_green_normal.png");
            button.x = cc.winSize.width / 2;
            button.y = cc.winSize.height / 2;
            this.addChild(button);
        }
    });

    var TestScene = cc.Scene.extend({
        ctor:function () {
            this._super();
        },
        onEnter:function () {
            this._super();
            var test_layer = new TestLayer();
            this.addChild(test_layer);
        }
    });

I tested with cocos-2d v3.10 and the upcoming v3.11. Same result.
And here what the button looks like in different browsers:

[ppawlak]

I am not sure if devs look at issues on this repo so I duplicated it on the cocos2d-x issue tracker : cocos2d/cocos2d-x#15565