Issue 1802 - Fix element hiding filters with multiple CSS selectors when using shadow DOM

include.preload.js

Index: include.preload.js
===================================================================
--- a/include.preload.js
+++ b/include.preload.js
@@ -152,6 +152,47 @@
   observer.observe(style.parentNode, {childList: true});
 }
 
+function convertSelectorsForShadowDOM(selectors)
+{
+  var result = [];
+  var prefix = "::content ";
+
+  for (var i = 0; i < selectors.length; i++)
+  {
+    var selector = selectors[i];
+    var start = 0;
+    var sep = "";
+
+    for (var j = 0; j < selector.length; j++)
+    {
+      var chr = selector[j];
+      switch (chr)
+      {
+        case "\\":
+          j++;
+          break;
+        case sep:
+          sep = "";
+          break;
+        case '"':
+        case "'":
+          sep = chr;
+          break;

[Wladimir Palant, 2015/01/22 08:15:52]

Note that technically there might be more separators: ( expects ), [ expects ].
However, I didn't find a scenario where an unescaped comma would be valid inside
parentheses, and that would also complicate things given that there could be
quoted strings inside.

+        case ",":
+          if (sep == "")
+          {
+            result.push(prefix + selector.substring(start, j));
+            start = j + 1;
+          }

[Wladimir Palant, 2015/01/22 08:15:52]

Nit: please add a break statement here, for consistency. Otherwise, if somebody
adds a new case statement they will need to remember doing that - and typically
people won't notice a missing break statement.

[Sebastian Noack, 2015/01/22 09:40:59]

Ah, let's go with if/else then. It's more compact, and seems to perform exactly
the same on Chrome.

+      }
+    }
+
+    result.push(prefix + selector.substring(start, j));

[Wladimir Palant, 2015/01/22 08:15:52]

The second parameter is unnecessary here, can be simply
selector.substring(start). Then you won't need to use the loop variable outside
the loop.

[Sebastian Noack, 2015/01/22 09:40:59]

Oh, you are right.

+  }
+
+  return result;
+}
+
 function init(document)
 {
   // Use Shadow DOM if available to don't mess with web pages that rely on
@@ -181,9 +222,7 @@
     if (shadow)
     {
       shadow.appendChild(style);
-
-      for (var i = 0; i < selectors.length; i++)
-        selectors[i] = "::content " + selectors[i];
+      selectors = convertSelectorsForShadowDOM(selectors);
     }
     else
     {