Issue 7104 - Clear style sheets when frame structure is updated

lib/contentFiltering.js

Index: lib/contentFiltering.js
===================================================================
--- a/lib/contentFiltering.js
+++ b/lib/contentFiltering.js
@@ -100,28 +100,29 @@
 
 function updateFrameStyles(tabId, frameId, styleSheet, groupName = "standard",
                            appendOnly = false)
 {
   let frame = ext.getFrame(tabId, frameId);
   if (!frame)
     return false;
 
-  if (!frame.injectedStyleSheets)
-    frame.injectedStyleSheets = new Map();
+  if (!frame.state.injectedStyleSheets)
+    frame.state.injectedStyleSheets = new Map();
 
-  let oldStyleSheet = frame.injectedStyleSheets.get(groupName);
+  let oldStyleSheet = frame.state.injectedStyleSheets.get(groupName);
 
   if (appendOnly && oldStyleSheet)
     styleSheet = oldStyleSheet + styleSheet;
 
   // Ideally we would compare the old and new style sheets and skip this code
-  // if they're the same, but the old style sheet can be a leftover from a
-  // previous instance of the frame. We must add the new style sheet
-  // regardless.
+  // if they're the same. But first we need to ensure that there are no edge
+  // cases that would cause the old style sheet to be a leftover from a
+  // previous instance of the frame (see issue #7180). For now, we add the new
+  // style sheet regardless.
 
   // Add the new style sheet first to keep previously hidden elements from
   // reappearing momentarily.
   if (styleSheet && !addStyleSheet(tabId, frameId, styleSheet))
     return false;
 
   // Sometimes the old and new style sheets can be exactly the same. In such a
   // case, do not remove the "old" style sheet, because it is in fact the new
@@ -129,17 +130,17 @@
   if (oldStyleSheet && oldStyleSheet != styleSheet)
     removeStyleSheet(tabId, frameId, oldStyleSheet);
 
   // The standard style sheet is ~660 KB per frame (as of Adblock Plus 3.3.2).
   // Keeping it in memory would only really be useful on Firefox, which allows
   // us to remove it via the tabs.removeCSS API. By choosing not to hold on to
   // it, we save potentially several megabytes per tab (#6967).
   if (groupName != "standard")
-    frame.injectedStyleSheets.set(groupName, styleSheet);
+    frame.state.injectedStyleSheets.set(groupName, styleSheet);
   return true;
 }
 
 function getExecutableCode(script)
 {
   let code = executableCode.get(script);
   if (code)
     return code;