diff --git a/layout/style/test/test_font_face_parser.html b/layout/style/test/test_font_face_parser.html
index b6b7cef3e202..7b817ba47432 100644
--- a/layout/style/test/test_font_face_parser.html
+++ b/layout/style/test/test_font_face_parser.html
@@ -29,18 +29,17 @@ function runTest() {
     { rule: "@font-face { ; }", d: {}, noncanonical: true },
 
     // Correct font-family.
-    { rule: _("font-family: \"Mouse\";"), d: {"font-family" : "\"Mouse\""} },
-    { rule: _("font-family: \"Mouse\""),  d: {"font-family" : "\"Mouse\""},
+    { rule: _("font-family: \"Mouse\";"), d: {"font-family" : "Mouse"},
       noncanonical: true },
-    { rule: _("font-family: Mouse;"),  d: {"font-family" : "Mouse" },
+    { rule: _("font-family: \"Mouse\""),  d: {"font-family" : "Mouse"},
       noncanonical: true },
+    { rule: _("font-family: Mouse;"),  d: {"font-family" : "Mouse" } },
     { rule: _("font-family: Mouse"),  d: {"font-family" : "Mouse" },
       noncanonical: true },
 
     // Correct but unusual font-family.
     { rule: _("font-family: Hoefler Text;"),
-      d: {"font-family" : "Hoefler Text"},
-      noncanonical: true },
+      d: {"font-family" : "Hoefler Text"} },
 
     // Incorrect font-family.
     { rule: _("font-family:"),        d: {} },
@@ -137,7 +136,7 @@ function runTest() {
       d: { "src" : "url(\"/fonts/Mouse\"), url(\"/fonts/Rat\")" } },
 
     { rule: _("src: local(Mouse), url(\"/fonts/Mouse\");"),
-      d: { "src" : "local(Mouse), url(\"/fonts/Mouse\")" },
+      d: { "src" : "local(\"Mouse\"), url(\"/fonts/Mouse\")" },
       noncanonical: true },
 
     { rule: _("src: local(\"老鼠\"), url(\"/fonts/Mouse\");"),
@@ -151,7 +150,7 @@ function runTest() {
 
     // Correct but unusual src:
     { rule: _("src: local(Hoefler Text);"),
-      d: {"src" : "local(Hoefler Text)"}, noncanonical: true },
+      d: {"src" : "local(\"Hoefler Text\")"}, noncanonical: true },
 
     // Incorrect src:
     { rule: _("src:"), d: {} },
@@ -173,15 +172,15 @@ function runTest() {
       d: { "src" : "url(\"/fonts/Mouse\")" },
       noncanonical: true },
     { rule: _("src: local(Cat); src: local(Mouse)"),
-      d: { "src" : "local(Mouse)" },
+      d: { "src" : "local(\"Mouse\")" },
       noncanonical: true },
 
     // Correct parenthesis matching for local()
     { rule: _("src: local(Mouse); src: local(Cat(); src: local(Rat); )"),
-      d: { "src" : "local(Mouse)" },
+      d: { "src" : "local(\"Mouse\")" },
       noncanonical: true },
     { rule: _("src: local(Mouse); src: local(\"Cat\"; src: local(Rat); )"),
-      d: { "src" : "local(Mouse)" },
+      d: { "src" : "local(\"Mouse\")" },
       noncanonical: true },
 
     // Correct parenthesis matching for format()
diff --git a/layout/style/test/test_font_family_serialization.html b/layout/style/test/test_font_family_serialization.html
index ad922158f5bc..996ef23d9177 100644
--- a/layout/style/test/test_font_family_serialization.html
+++ b/layout/style/test/test_font_family_serialization.html
@@ -6,12 +6,13 @@
 <div id="log"></div>
 <div id="display"></div>
 <script>
-// This cannot be a web-platform test because this doesn't match what
-// the spec says at the moment. Specifically, the spec wants to have
-// all font family serialized to string, while in practice, all browsers
-// serialize simple them to identifiers in some cases.
-// We want to check our current behavior. This can be changed once
-// browsers have an agreement on the exact behavior to spec.
+// Serialization of font-family names,
+// see https://github.com/w3c/csswg-drafts/issues/5846:
+//   - Quote if it matches an existing keyword (already required per spec).
+//   - Quote if it cannot be serialized as a keyword without escapes, e.g.:
+//     - contains non-alphanumeric ASCII;
+//     - contains a word that begins with a number.
+//   - Otherwise serialize as space-separated idents.
 
 // format: [input, expected serialization]
 const tests = [
@@ -20,7 +21,7 @@ const tests = [
   ['    simple    ', 'simple'],
   ['multi idents font', 'multi idents font'],
   ['    multi   idents   font    ', 'multi idents font'],
-  ['"wrapped name"', '"wrapped name"'],
+  ['"wrapped name"', 'wrapped name'],
   ['"   wrapped  name   "', '"   wrapped  name   "'],
 
   // Special whitespaces
@@ -33,7 +34,7 @@ const tests = [
   ['trailing ws\\   ', '"trailing ws "'],
   ['trailing ws   \\ ', '"trailing ws  "'],
   ['trailing ws\\ \\ ', '"trailing ws  "'],
-  ['escaped\\ ws', '"escaped ws"'],
+  ['escaped\\ ws', 'escaped ws'],
   ['escaped\\    ws', '"escaped  ws"'],
   ['escaped\\ \\ ws', '"escaped  ws"'],
   ['escaped   \\ ws', '"escaped  ws"'],