From a57b5c8ce52ceec656aca39928fcd9c294b10d29 Mon Sep 17 00:00:00 2001
From: Pascal Birchler <swissspidy@git.wordpress.org>
Date: Thu, 25 Feb 2016 10:22:43 +0000
Subject: [PATCH] Embeds: Use a more accessible way to initially hide the
 iframe.

This fixes a bug in Firefox where assets inside the iframe aren't being displayed because they have no computed style.

See #35894.

git-svn-id: https://develop.svn.wordpress.org/trunk@36708 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-includes/embed.php                   | 4 ++--
 src/wp-includes/js/wp-embed.js              | 2 +-
 tests/phpunit/tests/oembed/filterResult.php | 4 ++--
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/wp-includes/embed.php b/src/wp-includes/embed.php
index ff42351798..8c79cc8722 100644
--- a/src/wp-includes/embed.php
+++ b/src/wp-includes/embed.php
@@ -777,7 +777,7 @@ function wp_filter_oembed_result( $result, $data, $url ) {
 
 	if ( ! empty( $content[1] ) ) {
 		// We have a blockquote to fall back on. Hide the iframe by default.
-		$html = str_replace( '<iframe', '<iframe style="display:none;"', $html );
+		$html = str_replace( '<iframe', '<iframe style="position: absolute; clip: rect(1px, 1px, 1px, 1px);"', $html );
 		$html = str_replace( '<blockquote', '<blockquote class="wp-embedded-content"', $html );
 	}
 
@@ -953,7 +953,7 @@ function print_embed_scripts() {
  * @return string The filtered content.
  */
 function _oembed_filter_feed_content( $content ) {
-	return str_replace( '<iframe class="wp-embedded-content" sandbox="allow-scripts" security="restricted" style="display:none;"', '<iframe class="wp-embedded-content" sandbox="allow-scripts" security="restricted"', $content );
+	return str_replace( '<iframe class="wp-embedded-content" sandbox="allow-scripts" security="restricted" style="position: absolute; clip: rect(1px, 1px, 1px, 1px);"', '<iframe class="wp-embedded-content" sandbox="allow-scripts" security="restricted"', $content );
 }
 
 /**
diff --git a/src/wp-includes/js/wp-embed.js b/src/wp-includes/js/wp-embed.js
index 248ae2a36c..966a41f74a 100644
--- a/src/wp-includes/js/wp-embed.js
+++ b/src/wp-includes/js/wp-embed.js
@@ -50,7 +50,7 @@
 				continue;
 			}
 
-			source.style.display = '';
+			source.removeAttribute( 'style' );
 
 			/* Resize the iframe on request. */
 			if ( 'height' === data.message ) {
diff --git a/tests/phpunit/tests/oembed/filterResult.php b/tests/phpunit/tests/oembed/filterResult.php
index 10dc43b88c..7f29d5680a 100644
--- a/tests/phpunit/tests/oembed/filterResult.php
+++ b/tests/phpunit/tests/oembed/filterResult.php
@@ -83,14 +83,14 @@ EOD;
 		$html   = '<blockquote></blockquote><iframe></iframe>';
 		$actual = wp_filter_oembed_result( $html, (object) array( 'type' => 'rich' ), '' );
 
-		$this->assertEquals( '<blockquote class="wp-embedded-content"></blockquote><iframe class="wp-embedded-content" sandbox="allow-scripts" security="restricted" style="display:none;"></iframe>', $actual );
+		$this->assertEquals( '<blockquote class="wp-embedded-content"></blockquote><iframe class="wp-embedded-content" sandbox="allow-scripts" security="restricted" style="position: absolute; clip: rect(1px, 1px, 1px, 1px);"></iframe>', $actual );
 	}
 
 	function test_filter_oembed_result_allowed_html() {
 		$html   = '<blockquote class="foo" id="bar"><strong><a href="" target=""></a></strong></blockquote><iframe></iframe>';
 		$actual = wp_filter_oembed_result( $html, (object) array( 'type' => 'rich' ), '' );
 
-		$this->assertEquals( '<blockquote class="wp-embedded-content"><a href=""></a></blockquote><iframe class="wp-embedded-content" sandbox="allow-scripts" security="restricted" style="display:none;"></iframe>', $actual );
+		$this->assertEquals( '<blockquote class="wp-embedded-content"><a href=""></a></blockquote><iframe class="wp-embedded-content" sandbox="allow-scripts" security="restricted" style="position: absolute; clip: rect(1px, 1px, 1px, 1px);"></iframe>', $actual );
 	}
 
 	/**