diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-color-property-001-ref.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-color-property-001-ref.html
index 00c87eeb0625..43257f99e9c4 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-color-property-001-ref.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-color-property-001-ref.html
@@ -5,4 +5,4 @@
 <link rel="author" title="Mozilla" href="https://www.mozilla.org">
 <style> rt { font-variant-east-asian: inherit; } </style>
 <p>Pass if there is a <strong>green</strong> '&#x25CF;' above every character below:</p>
-<div style="line-height: 5; color: green"><ruby>試<rt>&#x25CF;</rt>験<rt>&#x25CF;</rt>テ<rt>&#x25CF;</rt>ス<rt>&#x25CF;</rt>ト<rt>&#x25CF;</rt></ruby></div>
+<div lang="ja" style="line-height: 5; color: green"><ruby>試<rt>&#x25CF;</rt>験<rt>&#x25CF;</rt>テ<rt>&#x25CF;</rt>ス<rt>&#x25CF;</rt>ト<rt>&#x25CF;</rt></ruby></div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-color-property-001.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-color-property-001.html
index 2d4676ad7090..347d2df95c4f 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-color-property-001.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-color-property-001.html
@@ -7,4 +7,4 @@
 <meta name="assert" content="The color of emphasis marks should be the same as the text by default">
 <link rel="match" href="text-emphasis-color-property-001-ref.html">
 <p>Pass if there is a <strong>green</strong> '&#x25CF;' above every character below:</p>
-<div style="line-height: 5; text-emphasis-style: filled circle; color: green">試験テスト</div>
+<div lang="ja" style="line-height: 5; text-emphasis-style: filled circle; color: green">試験テスト</div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-color-property-001a.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-color-property-001a.html
index 34c817e6815d..f4984d9a286d 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-color-property-001a.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-color-property-001a.html
@@ -7,4 +7,4 @@
 <meta name="assert" content="The color of emphasis marks should be the same as the text for initial value">
 <link rel="match" href="text-emphasis-color-property-001-ref.html">
 <p>Pass if there is a <strong>green</strong> '&#x25CF;' above every character below:</p>
-<div style="line-height: 5; text-emphasis-style: filled circle; text-emphasis-color: initial; color: green">試験テスト</div>
+<div lang="ja" style="line-height: 5; text-emphasis-style: filled circle; text-emphasis-color: initial; color: green">試験テスト</div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-color-property-001b.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-color-property-001b.html
index 0acb0f768296..a2bf1ca7ec2a 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-color-property-001b.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-color-property-001b.html
@@ -7,4 +7,4 @@
 <meta name="assert" content="The color of emphasis marks should be the same as the text by default">
 <link rel="match" href="text-emphasis-color-property-001-ref.html">
 <p>Pass if there is a <strong>green</strong> '&#x25CF;' above every character below:</p>
-<div style="line-height: 5; text-emphasis: filled circle; color: green">試験テスト</div>
+<div lang="ja" style="line-height: 5; text-emphasis: filled circle; color: green">試験テスト</div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-color-property-002-ref.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-color-property-002-ref.html
index 2bcc1d6b9bec..345d28739546 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-color-property-002-ref.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-color-property-002-ref.html
@@ -5,4 +5,4 @@
 <link rel="author" title="Mozilla" href="https://www.mozilla.org">
 <style> rt { font-variant-east-asian: inherit; color: green; } </style>
 <p>Pass if there is a <strong>green</strong> '&#x25CF;' above every character below:</p>
-<div style="line-height: 5;"><ruby>試<rt>&#x25CF;</rt>験<rt>&#x25CF;</rt>テ<rt>&#x25CF;</rt>ス<rt>&#x25CF;</rt>ト<rt>&#x25CF;</rt></ruby></div>
+<div lang="ja" style="line-height: 5;"><ruby>試<rt>&#x25CF;</rt>験<rt>&#x25CF;</rt>テ<rt>&#x25CF;</rt>ス<rt>&#x25CF;</rt>ト<rt>&#x25CF;</rt></ruby></div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-color-property-002.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-color-property-002.html
index a215267eb5b8..9d6419b3bbd2 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-color-property-002.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-color-property-002.html
@@ -7,4 +7,4 @@
 <meta name="assert" content="Emphasis marks should be rendered with color specified by text-emphasis-color.">
 <link rel="match" href="text-emphasis-color-property-002-ref.html">
 <p>Pass if there is a <strong>green</strong> '&#x25CF;' above every character below:</p>
-<div style="line-height: 5; text-emphasis-style: filled circle; text-emphasis-color: green">試験テスト</div>
+<div lang="ja" style="line-height: 5; text-emphasis-style: filled circle; text-emphasis-color: green">試験テスト</div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-line-height-001z.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-line-height-001z.html
index 81754d8789b2..dded6094e35b 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-line-height-001z.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-line-height-001z.html
@@ -17,4 +17,4 @@ textarea {
 }
 </style>
 <p>Pass if the emphasis marks are below the black line:</p>
-<textarea style="line-height: 1; border-top: 1px solid black; text-emphasis: circle;">試験テスト</textarea>
+<textarea lang="ja" style="line-height: 1; border-top: 1px solid black; text-emphasis: circle;">試験テスト</textarea>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-position-property-001-ref.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-position-property-001-ref.html
index a401c67beb1f..1121e1602f4a 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-position-property-001-ref.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-position-property-001-ref.html
@@ -5,4 +5,4 @@
 <link rel="author" title="Mozilla" href="https://www.mozilla.org">
 <style> rt { font-variant-east-asian: inherit; } </style>
 <p>Pass if the emphasis marks are over the text below:</p>
-<div style="line-height: 5;"><ruby>試<rt>&#x25CF;</rt>験<rt>&#x25CF;</rt>テ<rt>&#x25CF;</rt>ス<rt>&#x25CF;</rt>ト<rt>&#x25CF;</rt></ruby></div>
+<div lang="ja" style="line-height: 5;"><ruby>試<rt>&#x25CF;</rt>験<rt>&#x25CF;</rt>テ<rt>&#x25CF;</rt>ス<rt>&#x25CF;</rt>ト<rt>&#x25CF;</rt></ruby></div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-position-property-002-ref.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-position-property-002-ref.html
index 46659494783f..a0371c1f0313 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-position-property-002-ref.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-position-property-002-ref.html
@@ -5,4 +5,4 @@
 <link rel="author" title="Mozilla" href="https://www.mozilla.org">
 <style> rt { font-variant-east-asian: inherit; } </style>
 <p>Pass if the emphasis marks are under the text below:</p>
-<div style="line-height: 5; ruby-position: under"><ruby>試<rt>&#x25CF;</rt>験<rt>&#x25CF;</rt>テ<rt>&#x25CF;</rt>ス<rt>&#x25CF;</rt>ト<rt>&#x25CF;</rt></ruby></div>
+<div lang="ja" style="line-height: 5; ruby-position: under"><ruby>試<rt>&#x25CF;</rt>験<rt>&#x25CF;</rt>テ<rt>&#x25CF;</rt>ス<rt>&#x25CF;</rt>ト<rt>&#x25CF;</rt></ruby></div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-position-property-003-ref.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-position-property-003-ref.html
index 770fa1e8f5b2..9b0ad4d1e987 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-position-property-003-ref.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-position-property-003-ref.html
@@ -5,4 +5,4 @@
 <link rel="author" title="Mozilla" href="https://www.mozilla.org">
 <style> rt { font-variant-east-asian: inherit; } </style>
 <p>Pass if the emphasis marks are to the right of the text below:</p>
-<div style="line-height: 5; writing-mode: vertical-rl; ruby-position: over"><ruby>試<rt>&#x25CF;</rt>験<rt>&#x25CF;</rt>テ<rt>&#x25CF;</rt>ス<rt>&#x25CF;</rt>ト<rt>&#x25CF;</rt></ruby></div>
+<div lang="ja" style="line-height: 5; writing-mode: vertical-rl; ruby-position: over"><ruby>試<rt>&#x25CF;</rt>験<rt>&#x25CF;</rt>テ<rt>&#x25CF;</rt>ス<rt>&#x25CF;</rt>ト<rt>&#x25CF;</rt></ruby></div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-position-property-004-ref.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-position-property-004-ref.html
index 1e56f5877a9e..b82a758f8306 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-position-property-004-ref.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-position-property-004-ref.html
@@ -5,4 +5,4 @@
 <link rel="author" title="Mozilla" href="https://www.mozilla.org">
 <style> rt { font-variant-east-asian: inherit; } </style>
 <p>Pass if the emphasis marks are to the left of the text below:</p>
-<div style="line-height: 5; writing-mode: vertical-rl; ruby-position: under"><ruby>試<rt>&#x25CF;</rt>験<rt>&#x25CF;</rt>テ<rt>&#x25CF;</rt>ス<rt>&#x25CF;</rt>ト<rt>&#x25CF;</rt></ruby></div>
+<div lang="ja" style="line-height: 5; writing-mode: vertical-rl; ruby-position: under"><ruby>試<rt>&#x25CF;</rt>験<rt>&#x25CF;</rt>テ<rt>&#x25CF;</rt>ス<rt>&#x25CF;</rt>ト<rt>&#x25CF;</rt></ruby></div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-position-property-005-ref.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-position-property-005-ref.html
index 7427dec9d0a1..c6a6df1e03e1 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-position-property-005-ref.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-position-property-005-ref.html
@@ -5,4 +5,4 @@
 <link rel="author" title="Mozilla" href="https://www.mozilla.org">
 <style> rt { font-variant-east-asian: inherit; } </style>
 <p>Pass if the emphasis marks are to the right of the text below:</p>
-<div style="line-height: 5; writing-mode: vertical-rl; text-orientation: sideways; ruby-position: over"><ruby>試<rt>&#x25CF;</rt>験<rt>&#x25CF;</rt>テ<rt>&#x25CF;</rt>ス<rt>&#x25CF;</rt>ト<rt>&#x25CF;</rt></ruby></div>
+<div lang="ja" style="line-height: 5; writing-mode: vertical-rl; text-orientation: sideways; ruby-position: over"><ruby>試<rt>&#x25CF;</rt>験<rt>&#x25CF;</rt>テ<rt>&#x25CF;</rt>ス<rt>&#x25CF;</rt>ト<rt>&#x25CF;</rt></ruby></div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-position-property-006-ref.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-position-property-006-ref.html
index 85af6c250e22..b19d776410cd 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-position-property-006-ref.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-position-property-006-ref.html
@@ -5,4 +5,4 @@
 <link rel="author" title="Mozilla" href="https://www.mozilla.org">
 <style> rt { font-variant-east-asian: inherit; } </style>
 <p>Pass if the emphasis marks are to the left of the text below:</p>
-<div style="line-height: 5; writing-mode: vertical-rl; text-orientation: sideways; ruby-position: under"><ruby>試<rt>&#x25CF;</rt>験<rt>&#x25CF;</rt>テ<rt>&#x25CF;</rt>ス<rt>&#x25CF;</rt>ト<rt>&#x25CF;</rt></ruby></div>
+<div lang="ja" style="line-height: 5; writing-mode: vertical-rl; text-orientation: sideways; ruby-position: under"><ruby>試<rt>&#x25CF;</rt>験<rt>&#x25CF;</rt>テ<rt>&#x25CF;</rt>ス<rt>&#x25CF;</rt>ト<rt>&#x25CF;</rt></ruby></div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-property-001.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-property-001.html
index f45e2add8835..e208adc8242d 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-property-001.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-property-001.html
@@ -7,4 +7,4 @@
 <meta name="assert" content="text-emphasis: none does not produce any emphasis marks.">
 <link rel="match" href="text-emphasis-style-property-001-ref.html">
 <p>Pass if there is NO emphasis marks above the text below:</p>
-<div style="line-height: 5; text-emphasis: none">試験テスト</div>
+<div lang="ja" style="line-height: 5; text-emphasis: none">試験テスト</div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-property-002.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-property-002.html
index 0083d3e7a007..0048f4fd1418 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-property-002.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-property-002.html
@@ -7,4 +7,4 @@
 <meta name="assert" content="'text-emphasis: string' uses the given string as emphasis marks">
 <link rel="match" href="text-emphasis-style-property-002-ref.html">
 <p>Pass if there is a '^' above every character below:</p>
-<div style="line-height: 5; text-emphasis: '^'">試験テスト</div>
+<div lang="ja" style="line-height: 5; text-emphasis: '^'">試験テスト</div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-property-003.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-property-003.html
index fc35010e3ab7..cc564df57cea 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-property-003.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-property-003.html
@@ -7,4 +7,4 @@
 <meta name="assert" content="'text-emphasis: circle' produces U+25CF as emphasis marks.">
 <link rel="match" href="text-emphasis-style-property-012-ref.html">
 <p>Pass if there is a '&#x25CF;' above every character below:</p>
-<div style="line-height: 5; text-emphasis: circle">試験テスト</div>
+<div lang="ja" style="line-height: 5; text-emphasis: circle">試験テスト</div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-property-003a.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-property-003a.html
index e70518b06249..313cf0ee1766 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-property-003a.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-property-003a.html
@@ -7,4 +7,4 @@
 <meta name="assert" content="'text-emphasis: filled' produces U+25CF as emphasis marks.">
 <link rel="match" href="text-emphasis-style-property-012-ref.html">
 <p>Pass if there is a '&#x25CF;' above every character below:</p>
-<div style="line-height: 5; text-emphasis: filled">試験テスト</div>
+<div lang="ja" style="line-height: 5; text-emphasis: filled">試験テスト</div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-property-003b.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-property-003b.html
index 79e66bc93a22..c90d455126d5 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-property-003b.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-property-003b.html
@@ -7,4 +7,4 @@
 <meta name="assert" content="'text-emphasis: filled circle' produces U+25CF as emphasis marks.">
 <link rel="match" href="text-emphasis-style-property-012-ref.html">
 <p>Pass if there is a '&#x25CF;' above every character below:</p>
-<div style="line-height: 5; text-emphasis: filled circle">試験テスト</div>
+<div lang="ja" style="line-height: 5; text-emphasis: filled circle">試験テスト</div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-property-004.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-property-004.html
index 15d2ab001cc1..6af2210d22d3 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-property-004.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-property-004.html
@@ -7,4 +7,4 @@
 <meta name="assert" content="Emphasis marks should be rendered with color specified by text-emphasis.">
 <link rel="match" href="text-emphasis-color-property-002-ref.html">
 <p>Pass if there is a <strong>green</strong> '&#x25CF;' above every character below:</p>
-<div style="line-height: 5; text-emphasis: circle green">試験テスト</div>
+<div lang="ja" style="line-height: 5; text-emphasis: circle green">試験テスト</div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-property-004a.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-property-004a.html
index 6d0d80d29419..23039ae6ced5 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-property-004a.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-property-004a.html
@@ -7,4 +7,4 @@
 <meta name="assert" content="Emphasis marks should be rendered with color specified by text-emphasis.">
 <link rel="match" href="text-emphasis-color-property-002-ref.html">
 <p>Pass if there is a <strong>green</strong> '&#x25CF;' above every character below:</p>
-<div style="line-height: 5; text-emphasis: green circle">試験テスト</div>
+<div lang="ja" style="line-height: 5; text-emphasis: green circle">試験テスト</div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-001-ref.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-001-ref.html
index 60f8fa7b95cd..9dc6c897cf4b 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-001-ref.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-001-ref.html
@@ -4,4 +4,4 @@
 <link rel="author" title="Xidorn Quan" href="https://www.upsuper.org">
 <link rel="author" title="Mozilla" href="https://www.mozilla.org">
 <p>Pass if there is NO emphasis marks above the text below:</p>
-<div style="line-height: 5;">試験テスト</div>
+<div lang="ja" style="line-height: 5;">試験テスト</div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-001.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-001.html
index 910293b44a32..e2bc386afd6b 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-001.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-001.html
@@ -7,4 +7,4 @@
 <meta name="assert" content="text-emphasis-style: none does not produce any emphasis marks.">
 <link rel="match" href="text-emphasis-style-property-001-ref.html">
 <p>Pass if there is NO emphasis marks above the text below:</p>
-<div style="line-height: 5; text-emphasis-style: none">試験テスト</div>
+<div lang="ja" style="line-height: 5; text-emphasis-style: none">試験テスト</div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-002-ref.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-002-ref.html
index e9cf74415ce8..10504677c72c 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-002-ref.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-002-ref.html
@@ -5,4 +5,4 @@
 <link rel="author" title="Mozilla" href="https://www.mozilla.org">
 <style> rt { font-variant-east-asian: normal; } </style>
 <p>Pass if there is a '^' above every character below:</p>
-<div style="line-height: 5"><ruby>試<rt>^</rt>験<rt>^</rt>テ<rt>^</rt>ス<rt>^</rt>ト<rt>^</rt></ruby></div>
+<div lang="ja" style="line-height: 5"><ruby>試<rt>^</rt>験<rt>^</rt>テ<rt>^</rt>ス<rt>^</rt>ト<rt>^</rt></ruby></div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-002.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-002.html
index dc0496653d1a..20162842a843 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-002.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-002.html
@@ -7,4 +7,4 @@
 <meta name="assert" content="'text-emphasis-style: string' uses the given string as emphasis marks">
 <link rel="match" href="text-emphasis-style-property-002-ref.html">
 <p>Pass if there is a '^' above every character below:</p>
-<div style="line-height: 5; text-emphasis-style: '^'">試験テスト</div>
+<div lang="ja" style="line-height: 5; text-emphasis-style: '^'">試験テスト</div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-003-ref.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-003-ref.html
index d0c558d19794..fadc7d2773ea 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-003-ref.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-003-ref.html
@@ -5,4 +5,4 @@
 <link rel="author" title="Mozilla" href="https://www.mozilla.org">
 <style> rt { font-variant-east-asian: normal; } </style>
 <p>Pass if there is a '&#xFE45;' to the right of every character below:</p>
-<div style="writing-mode: vertical-rl; line-height: 5;"><ruby>試<rt>&#xFE45;</rt>験<rt>&#xFE45;</rt>テ<rt>&#xFE45;</rt>ス<rt>&#xFE45;</rt>ト<rt>&#xFE45;</rt></ruby></div>
+<div lang="ja" style="writing-mode: vertical-rl; line-height: 5;"><ruby>試<rt>&#xFE45;</rt>験<rt>&#xFE45;</rt>テ<rt>&#xFE45;</rt>ス<rt>&#xFE45;</rt>ト<rt>&#xFE45;</rt></ruby></div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-003.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-003.html
index b2af7448f1d7..4bfcffffa2e0 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-003.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-003.html
@@ -7,4 +7,4 @@
 <meta name="assert" content="'text-emphasis-style: filled' produces U+FE45 as emphasis marks in vertical writing modes.">
 <link rel="match" href="text-emphasis-style-property-003-ref.html">
 <p>Pass if there is a '&#xFE45;' to the right of every character below:</p>
-<div style="writing-mode: vertical-rl; line-height: 5; text-emphasis-style: filled">試験テスト</div>
+<div lang="ja" style="writing-mode: vertical-rl; line-height: 5; text-emphasis-style: filled">試験テスト</div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-004-ref.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-004-ref.html
index 493f0c67364d..d89ae5a5c871 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-004-ref.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-004-ref.html
@@ -5,4 +5,4 @@
 <link rel="author" title="Mozilla" href="https://www.mozilla.org">
 <style> rt { font-variant-east-asian: normal; } </style>
 <p>Pass if there is a '&#xFE46;' to the right of every character below:</p>
-<div style="writing-mode: vertical-rl; line-height: 5;"><ruby>試<rt>&#xFE46;</rt>験<rt>&#xFE46;</rt>テ<rt>&#xFE46;</rt>ス<rt>&#xFE46;</rt>ト<rt>&#xFE46;</rt></ruby></div>
+<div lang="ja" style="writing-mode: vertical-rl; line-height: 5;"><ruby>試<rt>&#xFE46;</rt>験<rt>&#xFE46;</rt>テ<rt>&#xFE46;</rt>ス<rt>&#xFE46;</rt>ト<rt>&#xFE46;</rt></ruby></div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-004.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-004.html
index 06fc2fd7c361..360b0357c244 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-004.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-004.html
@@ -7,4 +7,4 @@
 <meta name="assert" content="'text-emphasis: open sesame' produces U+FE46 as emphasis marks.">
 <link rel="match" href="text-emphasis-style-property-004-ref.html">
 <p>Pass if there is a '&#xFE46;' to the right of every character below:</p>
-<div style="writing-mode: vertical-rl; line-height: 5; text-emphasis-style: open">試験テスト</div>
+<div lang="ja" style="writing-mode: vertical-rl; line-height: 5; text-emphasis-style: open">試験テスト</div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-005-ref.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-005-ref.html
index b65490267033..361591860adc 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-005-ref.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-005-ref.html
@@ -5,4 +5,4 @@
 <link rel="author" title="Mozilla" href="https://www.mozilla.org">
 <style> rt { font-variant-east-asian: normal; text-orientation: upright; } </style>
 <p>Pass if the emphasis marks 'V' are upright:</p>
-<div style="writing-mode: vertical-rl; line-height: 5;"><ruby>試<rt>V</rt>験<rt>V</rt>テ<rt>V</rt>ス<rt>V</rt>ト<rt>V</rt></ruby></div>
+<div lang="ja" style="writing-mode: vertical-rl; line-height: 5;"><ruby>試<rt>V</rt>験<rt>V</rt>テ<rt>V</rt>ス<rt>V</rt>ト<rt>V</rt></ruby></div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-005.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-005.html
index 29be3abda073..fc8ae4e46135 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-005.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-005.html
@@ -7,4 +7,4 @@
 <meta name="assert" content="Emphasis marks must remain upright in vertical writing modes">
 <link rel="match" href="text-emphasis-style-property-005-ref.html">
 <p>Pass if the emphasis marks 'V' are upright:</p>
-<div style="writing-mode: vertical-rl; line-height: 5; text-emphasis-style: 'V'">試験テスト</div>
+<div lang="ja" style="writing-mode: vertical-rl; line-height: 5; text-emphasis-style: 'V'">試験テスト</div>
diff --git a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-005a.html b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-005a.html
index af0ad4e0aa72..3ea24ba611a4 100644
--- a/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-005a.html
+++ b/layout/reftests/w3c-css/submitted/text-decor-3/text-emphasis-style-property-005a.html
@@ -7,4 +7,4 @@
 <meta name="assert" content="Emphasis marks must remain upright in vertical writing modes">
 <link rel="match" href="text-emphasis-style-property-005-ref.html">
 <p>Pass if the emphasis marks 'V' are upright:</p>
-<div style="writing-mode: vertical-lr; line-height: 5; text-emphasis-style: 'V'">試験テスト</div>
+<div lang="ja" style="writing-mode: vertical-lr; line-height: 5; text-emphasis-style: 'V'">試験テスト</div>