Issue 6999 - Generate style sheets in background page

lib/contentFiltering.js

Index: lib/contentFiltering.js
===================================================================
--- a/lib/contentFiltering.js
+++ b/lib/contentFiltering.js
@@ -40,37 +40,43 @@
 
 let userStyleSheetsSupported = true;
 
 let snippetsLibrarySource = "";
 let executableCode = new Map();
 
 function addStyleSheet(tabId, frameId, styleSheet)
 {
+  let details = {
+    code: styleSheet,
+    frameId,
+    matchAboutBlank: true,
+    runAt: "document_start"
+  };
+
+  if (userStyleSheetsSupported)
+    details.cssOrigin = "user";
+
   try
   {
-    let promise = browser.tabs.insertCSS(tabId, {
-      code: styleSheet,
-      cssOrigin: "user",
-      frameId,
-      matchAboutBlank: true,
-      runAt: "document_start"
-    });
-
     // See error handling notes in the catch block.
-    promise.catch(() => {});
+    browser.tabs.insertCSS(tabId, details).catch(() => {});
   }
   catch (error)
   {
     // If the error is about the "cssOrigin" option, this is an older version
     // of Chromium (65 and below) or Firefox (52 and below) that does not
     // support user style sheets.
-    if (/\bcssOrigin\b/.test(error.message))
+    if (userStyleSheetsSupported && /\bcssOrigin\b/.test(error.message))
+    {
       userStyleSheetsSupported = false;
 
+      return addStyleSheet(tabId, frameId, styleSheet);
+    }
+
     // For other errors, we simply return false to indicate failure.
     //
     // One common error that occurs frequently is when a frame is not found
     // (e.g. "Error: No frame with id 574 in tab 266"), which can happen when
     // the code in the parent document has removed the frame before the
     // background page has had a chance to respond to the content script's
     // "content.applyFilters" message. We simply ignore such errors, because
     // otherwise they show up in the log too often and make debugging
@@ -194,17 +200,16 @@
   }
 }
 
 port.on("content.applyFilters", (message, sender) =>
 {
   let selectors = [];
   let emulatedPatterns = [];
   let trace = HitLogger.hasListener(sender.page.id);
-  let inline = !userStyleSheetsSupported;
 
   let {elemhide, snippets} = message.filterTypes ||
                              {elemhide: true, snippets: true};
 
   if (!checkWhitelisted(sender.page, sender.frame, null,
                         RegExpFilter.typeMap.DOCUMENT))
   {
     let docDomain = extractHostFromFrame(sender.frame);
@@ -235,33 +240,22 @@
                                           RegExpFilter.typeMap.GENERICHIDE);
       selectors = ElemHide.getSelectorsForDomain(docDomain, specificOnly);
 
       for (let filter of ElemHideEmulation.getRulesForDomain(docDomain))
         emulatedPatterns.push({selector: filter.selector, text: filter.text});
     }
   }
 
-  if (!inline && !updateFrameStyles(sender.page.id, sender.frame.id,
-                                    selectors, "standard"))
-  {
-    inline = true;
-  }
+  updateFrameStyles(sender.page.id, sender.frame.id, selectors, "standard");
 
-  let response = {trace, inline, emulatedPatterns};
-  if (trace || inline)
+  let response = {trace, emulatedPatterns};
+  if (trace)
     response.selectors = selectors;
 
-  // If we can't remove user style sheets using tabs.removeCSS, we'll only keep
-  // adding them, which could cause problems with emulation filters as
-  // described in issue #5864. Instead, we can just ask the content script to
-  // add styles for emulation filters inline.
-  if (!styleSheetRemovalSupported)
-    response.inlineEmulated = true;
-
   return response;
 });
 
 port.on("elemhide.injectSelectors", (message, sender) =>
 {
   updateFrameStyles(sender.page.id, sender.frame.id, message.selectors,
                     message.groupName, message.appendOnly);
 });