Correct an Opal v1.4 compatibility issue

Author: hmdne

opal/browser/support.rb

@@ -75,14 +75,16 @@ def self.supports?(feature)
       when 'Window.send (Asynchronous)'
         if defined?(`window.postMessage`) && !defined?(`window.importScripts`)
           %x{
-            var ok  = true,
-                old = window.onmessage;
+            (function() {
+              var ok  = true,
+                  old = window.onmessage;
 
-            window.onmessage = function() { ok = false; };
-            window.postMessage("", "*")
-            window.onmessage = old;
+              window.onmessage = function() { ok = false; };
+              window.postMessage("", "*")
+              window.onmessage = old;
 
-            return ok;
+              return ok;
+            })()
           }
         end
 
@@ -106,45 +108,55 @@ def self.supports?(feature)
 
       when 'Attr.isId'
         %x{
-          var div = document.createElement('div');
-              div.setAttribute('id', 'xxxxxxxxxxxxx');
+          (function() {
+            var div = document.createElement('div');
+                div.setAttribute('id', 'xxxxxxxxxxxxx');
 
-          return typeof(div.attributes['id'].isId) !== "undefined";
+            return typeof(div.attributes['id'].isId) !== "undefined";
+          })()
         }
 
       when 'Element.addBehavior'
         defined?(`document.documentElement.addBehavior`)
 
       when 'Element.className'
         %x{
-          var div = document.createElement("div");
-              div.setAttribute('className', 'x');
+          (function() {
+            var div = document.createElement("div");
+                div.setAttribute('className', 'x');
 
-          return div.className === 'x';
+            return div.className === 'x';
+          })()
         }
 
       when 'Element.class'
         %x{
-          var div = document.createElement("div");
-              div.setAttribute('class', 'x');
+          (function() {
+            var div = document.createElement("div");
+                div.setAttribute('class', 'x');
 
-          return div.className === 'x';
+            return div.className === 'x';
+          })()
         }
 
       when 'Element.for'
         %x{
-          var label = document.createElement("label");
-              label.setAttribute('for', 'x');
+          (function() {
+            var label = document.createElement("label");
+                label.setAttribute('for', 'x');
 
-          return label.htmlFor === 'x';
+            return label.htmlFor === 'x';
+          })()
         }
 
       when 'Element.htmlFor'
         %x{
-          var label = document.createElement("label");
-              label.setAttribute('htmlFor', 'x');
+          (function() {
+            var label = document.createElement("label");
+                label.setAttribute('htmlFor', 'x');
 
-          return label.htmlFor === 'x';
+            return label.htmlFor === 'x';
+          })()
         }
 
       when 'Element.clientSize'