Centering text inside a button set to display flex with justify-content: center is impossible

Source/core/rendering/RenderButton.cpp

 /**
  * Copyright (C) 2005 Apple Computer, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 79 matching lines @@
 {
     ASSERT(innerStyle->refCount() == 1);
     // RenderBlock::createAnonymousBlock creates a new RenderStyle, so this is
     // safe to modify.
     innerStyle->setFlexGrow(1.0f);
     // Use margin:auto instead of align-items:center to get safe centering, i.e.
     // when the content overflows, treat it the same as align-items: flex-start.
     innerStyle->setMarginTop(Length());
     innerStyle->setMarginBottom(Length());
     innerStyle->setFlexDirection(style()->flexDirection());
+    innerStyle->setJustifyContent(style()->justifyContent());
+    innerStyle->setFlexWrap(style()->flexWrap());
+    innerStyle->setAlignItems(style()->alignItems());
+    innerStyle->setAlignContent(style()->alignContent());
 }
 
 bool RenderButton::canHaveGeneratedChildren() const
 {
     // Input elements can't have generated children, but button elements can. We'll
     // write the code assuming any other button types that might emerge in the future
     // can also have children.
     return !isHTMLInputElement(*node());
 }
 
@@ skipping 15 matching lines @@
         // baseline for the empty case manually here.
         if (direction == HorizontalLine)
             return marginTop() + borderTop() + paddingTop() + contentHeight();
 
         return marginRight() + borderRight() + paddingRight() + contentWidth();
     }
     return RenderFlexibleBox::baselinePosition(baseline, firstLine, direction, linePositionMode);
 }
 
 } // namespace WebCore