Bug 1871745 - Keep exposing chrome-only properties on CSS2Properties. r=peterv

So that chrome code can keep setting -moz-user-focus via script, for
example.

Differential Revision: https://phabricator.services.mozilla.com/D197295

browser/base/content/browser.js

@@ -10051,13 +10051,10 @@ var FirefoxViewHandler = {
         this.button?.setAttribute("aria-pressed", selected);
         this._recordViewIfTabSelected();
         this._onTabForegrounded();
-        if (e.target == this.tab) {
-          // If Fx View is opened, add temporary style to make first available tab focusable
-          gBrowser.visibleTabs[0].style["-moz-user-focus"] = "normal";
-        } else {
-          // When Fx View is closed, remove temporary -moz-user-focus style from first available tab
-          gBrowser.visibleTabs[0].style.removeProperty("-moz-user-focus");
-        }
+        // If Fx View is opened, add temporary style to make first available tab focusable
+        // When Fx View is closed, remove temporary -moz-user-focus style from first available tab
+        gBrowser.visibleTabs[0].style.MozUserFocus =
+          e.target == this.tab ? "normal" : "";
         break;
       case "TabClose":
         this.tab = null;

dom/bindings/Configuration.py

@@ -382,11 +382,12 @@ class Configuration(DescriptorProvider):
 
             def filterExtendedAttributes(extendedAttributes):
                 # These are the extended attributes that we allow to have
-                # different values among all atributes that use the same
+                # different values among all attributes that use the same
                 # template.
                 ignoredAttributes = {
                     "BindingTemplate",
                     "BindingAlias",
+                    "ChromeOnly",
                     "Pure",
                     "Pref",
                     "Func",

dom/bindings/GenerateCSS2PropertiesWebIDL.py

@@ -23,9 +23,6 @@ def generate(output, idlFilename, dataFile):
     propsData = runpy.run_path(dataFile)["data"]
     props = ""
     for p in propsData.values():
-        if "Internal" in p.flags:
-            continue
-
         # Skip properties which aren't valid in style rules.
         if "Style" not in p.rules:
             continue
@@ -46,6 +43,7 @@ def generate(output, idlFilename, dataFile):
         ]
 
         if p.pref != "":
+            assert "Internal" not in p.flags
             # BackdropFilter is a special case where we want WebIDL to check
             # a function instead of checking the pref directly.
             if p.method == "BackdropFilter":
@@ -54,6 +52,10 @@ def generate(output, idlFilename, dataFile):
             # see bug 1861828, 1865332, 1860424, 1864970, 1865332, 1869119.
             elif p.method not in ["MozTransform", "MozTransformOrigin"]:
                 extendedAttrs.append('Pref="%s"' % p.pref)
+        elif "EnabledInUASheetsAndChrome" in p.flags:
+            extendedAttrs.append("ChromeOnly")
+        elif "Internal" in p.flags:
+            continue
 
         def add_extra_accessors(p):
             prop = p.method

layout/style/test/test_non_content_accessible_properties.html

@@ -4,26 +4,30 @@
 <iframe></iframe>
 <iframe srcdoc="Foo"></iframe>
 <script>
-const NON_CONTENT_ACCESSIBLE_PROPERTIES = [
-  "-x-span",
-  "-x-lang",
-  "-x-text-scale",
+const CHROME_ONLY_PROPERTIES = [
   "-moz-window-input-region-margin",
   "-moz-window-shadow",
   "-moz-window-opacity",
   "-moz-window-transform",
   "-moz-window-transform-origin",
+  "-moz-default-appearance",
+  "-moz-user-focus",
+];
+
+const UA_ONLY_PROPERTIES = [
+  "-x-span",
+  "-x-lang",
+  "-x-text-scale",
+  "-moz-control-character-visibility",
   "-moz-top-layer",
   "-moz-script-level",
   "-moz-math-display",
   "-moz-math-variant",
-  "-moz-font-smoothing-background-color",
-  "-moz-min-font-size-ratio",
-  "-moz-default-appearance",
   "-moz-inert",
-  "-moz-control-character-visibility",
+  "-moz-min-font-size-ratio",
+  // TODO: This should ideally be in CHROME_ONLY_PROPERTIES, but due to how
+  // [Pref] and [ChromeOnly] interact in WebIDL, the former wins.
   "-moz-context-properties",
-  "-moz-user-focus",
 ];
 
 function testInWin(win) {
@@ -36,9 +40,14 @@ function testInWin(win) {
   sheet.textContent = `div { color: initial }`;
   assert_equals(sheet.sheet.cssRules[0].style.length, 1, `sanity: ${doc.documentURI}`);
 
-  for (const prop of NON_CONTENT_ACCESSIBLE_PROPERTIES) {
+  for (const prop of CHROME_ONLY_PROPERTIES.concat(UA_ONLY_PROPERTIES)) {
     sheet.textContent = `div { ${prop}: initial }`;
     let block = sheet.sheet.cssRules[0].style;
+    assert_false(prop in block, `${prop} shouldn't be exposed in CSS2Properties`);
+
+    let isUAOnly = UA_ONLY_PROPERTIES.includes(prop);
+    assert_equals(prop in SpecialPowers.wrap(block), !isUAOnly, `${prop} should be exposed to chrome code if needed`);
+
     assert_equals(
       block.length,
       0,