Add USw hook to remove get stylus button (#1239)

background/navigation-manager.js

@@ -66,6 +66,21 @@ bgReady.all.then(() => {
       {hostEquals: 'sleazyfork.org', urlMatches},
     ],
   });
+
+  /*
+   * Removes the Get Stylus button on style pages.
+   * Not using manifest.json as adding a content script disables the extension on update.
+   */
+  chrome.webNavigation.onCommitted.addListener(({tabId}) => {
+    chrome.tabs.executeScript(tabId, {
+      file: '/content/install-hook-userstylesworld.js',
+      runAt: 'document_start',
+    });
+  }, {
+    url: [
+      {hostEquals: 'userstyles.world'},
+    ],
+  });
   /*
    * FF misses some about:blank iframes so we inject our content script explicitly
    */

content/install-hook-userstylesworld.js

@@ -0,0 +1,22 @@
+'use strict';
+
+(() => {
+  const allowedOrigin = 'https://userstyles.world';
+
+  const sendPostMessage = message => {
+    if (allowedOrigin === location.origin) {
+      window.postMessage(message, location.origin);
+    }
+  };
+
+  const onPageLoaded = event => {
+    if (event.data
+    && event.data.type === 'usw-ready'
+    && allowedOrigin === event.origin
+    ) {
+      sendPostMessage({type: 'usw-remove-stylus-button'});
+    }
+  };
+
+  window.addEventListener('message', onPageLoaded);
+})();