From 5fd43eaab3bb98ed249771d961c2dbe132bcf2b5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Emilio=20Cobos=20=C3=81lvarez?= <emilio@crisal.io>
Date: Fri, 24 Jun 2022 00:04:18 +0000
Subject: [PATCH] Bug 1776157 - Don't force chrome frames to be opaque.
 r=dholbert

It causes unnecessary flashes in some cases, like the sidebar which
intentionally loads about:blank.

Differential Revision: https://phabricator.services.mozilla.com/D150096
---
 layout/base/PresShell.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/layout/base/PresShell.cpp b/layout/base/PresShell.cpp
index a1e4175de5eaf..8cd1cee03620a 100644
--- a/layout/base/PresShell.cpp
+++ b/layout/base/PresShell.cpp
@@ -5378,6 +5378,9 @@ void PresShell::AddCanvasBackgroundColorItem(
 bool PresShell::IsTransparentContainerElement() const {
   nsPresContext* pc = GetPresContext();
   if (!pc->IsRootContentDocumentCrossProcess()) {
+    if (pc->IsChrome()) {
+      return true;
+    }
     // Frames are transparent except if their embedder color-scheme is
     // mismatched, in which case we use an opaque background to avoid
     // black-on-black or white-on-white text, see