Issue 3163 - Adapt "Block element" functionality for a change in Chrome dealing with "\0" in CSS se…

lib/filterComposer.js

Index: lib/filterComposer.js
===================================================================
--- a/lib/filterComposer.js
+++ b/lib/filterComposer.js
@@ -22,6 +22,10 @@
 let {defaultMatcher} = require("matcher");
 let {RegExpFilter} = require("filterClasses");
 
+function isValidString(s) {
+  return s && s.indexOf("\0") == -1;
+}
+
 function escapeChar(chr)
 {
   let code = chr.charCodeAt(0);
@@ -119,19 +123,21 @@
     if (filters.length == 0 && !isFrameWhitelisted(page, frame, RegExpFilter.typeMap.ELEMHIDE))
     {
       // Generate CSS selectors based on the element's "id" and "class" attribute
-      if (details.id)
+      if (isValidString(details.id))
         selectors.push("#" + escapeCSS(details.id));
-      if (details.classes.length > 0)
-        selectors.push(details.classes.map(c => "." + escapeCSS(c)).join(""));
+
+      let classes = details.classes.filter(isValidString);
+      if (classes.length > 0)
+        selectors.push(classes.map(c => "." + escapeCSS(c)).join(""));
 
       // If there is a "src" attribute, specifiying a URL that we can't block,
       // generate a CSS selector matching the "src" attribute
-      if (details.src)
+      if (isValidString(details.src))
         selectors.push(escapeCSS(details.tagName) + "[src=" + quoteCSS(details.src) + "]");
 
       // As last resort, if there is a "style" attribute, and we couldn't generate
       // any filters so far, generate a CSS selector matching the "style" attribute
-      if (details.style && selectors.length == 0 && filters.length == 0)
+      if (isValidString(details.style) && selectors.length == 0 && filters.length == 0)
         selectors.push(escapeCSS(details.tagName) + "[style=" + quoteCSS(details.style) + "]");
 
       // Add an element hiding filter for each generated CSS selector