[DevTools] prevent StyleX plugin from throwing when inspecting CSS (#…

…26364)

## Summary

An error might happen when we try to read the CSS rules, but the
stylesheet does not allow so (often happens on production).

Before:
<img width="713" alt="image"
src="https://user-images.githubusercontent.com/1001890/224376546-024f7a32-d314-4dd1-9333-7e47d96a2b7c.png">

After:

<img width="504" alt="image"
src="https://user-images.githubusercontent.com/1001890/224376426-964a33c4-0677-4a51-91c2-74074e4dde63.png">


## How did you test this change?

Built a fb version and tested locally (see above screenshot)

---------

Co-authored-by: Hendrik Liebau <mail@hendrik-liebau.de>

packages/react-devtools-shared/src/backend/StyleX/utils.js

@@ -67,7 +67,10 @@ function crawlObjectProperties(
         // Special case; this key is the name of the style's source/file/module.
         sources.add(key);
       } else {
-        resolvedStyles[key] = getPropertyValueForStyleName(value);
+        const propertyValue = getPropertyValueForStyleName(value);
+        if (propertyValue != null) {
+          resolvedStyles[key] = propertyValue;
+        }
       }
     } else {
       const nestedStyle = {};
@@ -90,13 +93,19 @@ function getPropertyValueForStyleName(styleName: string): string | null {
     const styleSheet = ((document.styleSheets[
       styleSheetIndex
     ]: any): CSSStyleSheet);
-    // $FlowFixMe Flow doesn't konw about these properties
-    const rules = styleSheet.rules || styleSheet.cssRules;
-    // $FlowFixMe `rules` is mixed
+    let rules: CSSRuleList | null = null;
+    // this might throw if CORS rules are enforced https://www.w3.org/TR/cssom-1/#the-cssstylesheet-interface
+    try {
+      rules = styleSheet.cssRules;
+    } catch (_e) {
+      continue;
+    }
+
     for (let ruleIndex = 0; ruleIndex < rules.length; ruleIndex++) {
-      // $FlowFixMe `rules` is mixed
-      const rule = rules[ruleIndex];
-      // $FlowFixMe Flow doesn't konw about these properties
+      if (!(rules[ruleIndex] instanceof CSSStyleRule)) {
+        continue;
+      }
+      const rule = ((rules[ruleIndex]: any): CSSStyleRule);
       const {cssText, selectorText, style} = rule;
 
       if (selectorText != null) {