fix(devtools): prevent devTools to load when not text/html document (a…

…ngular#48021)

On Firefox, Angular DevTools was breaking the XML display because of the script injected
Based on contentType, we won't inject that script anymore

Fixes angular#48017

PR Close angular#48021

devtools/projects/shell-browser/src/app/ng-validate.ts

@@ -14,7 +14,9 @@ window.addEventListener('message', (event: MessageEvent) => {
   }
 });
 
-const script = document.createElement('script');
-script.src = chrome.runtime.getURL('app/detect_angular_for_extension_icon_bundle.js');
-document.documentElement.appendChild(script);
-document.documentElement.removeChild(script);
+if (document.contentType === 'text/html') {
+  const script = document.createElement('script');
+  script.src = chrome.runtime.getURL('app/detect_angular_for_extension_icon_bundle.js');
+  document.documentElement.appendChild(script);
+  document.documentElement.removeChild(script);
+}