Voting: Replace temporary fix for IE11.

Commit d9daaaf added a temporary fix for errors introduced in commit 5c3f569 that
caused reddit to break in some browsers, most notably IE11. This improves upon
that fix by reducing the amount of code in try/catch blocks to only the known
sources of errors, and adding some safegaurds to catch other potential errors.

r2/r2/lib/js.py

@@ -440,10 +440,10 @@ module["reddit-init-base"] = LocalizedModule("reddit-init-base.js",
     "lib/jquery.cookie.js",
     "bootstrap.tooltip.extension.js",
     "base.js",
-    "voting.js",
     "preload.js",
     "logging.js",
     "client-error-logger.js",
+    "voting.js",
     "jquery.html-patch.js",
     "uibase.js",
     "i18n.js",

r2/r2/public/static/js/voting.js

@@ -2,34 +2,49 @@
   var UP_CLS = "up";
   var DOWN_CLS = "down";
   var theFakeClick;
-  var MouseEvent;
-  var createEvent;
-  
-  try {
-    MouseEvent = window.MouseEvent;
-    createEvent = document.createEvent.bind(document);
+  var MouseEvent = window.MouseEvent;
+  var createEvent = document.createEvent;
 
+  if (createEvent) {
+    // document.createEvent throws if not called from document;
+    createEvent = createEvent.bind(document);
+  }
+
+  try {
+    // Some browsers (e.g. IE11) throw an error here.
     if (MouseEvent) {
       theFakeClick = new MouseEvent('click', {bubbles: true});
-    } else if (createEvent) {
-      theFakeClick = createEvent('MouseEvent');
-    } else {
-      theFakeClick = {};
-    }
-
-    window.MouseEvent = function(type, init) {
-      return theFakeClick;
-    }
-
-    document.createEvent = function(type) {
-      if (type === 'MouseEvent' || type === 'MouseEvents') {
-        return theFakeClick;
-      } else {
-        return createEvent(type);
-      }
     }
   } catch (e) {
-    // something went wrong
+    // We'll handle this below as if MouseEvent doesn't exist.
+  }
+
+  try {
+    // To be on the safe side, we'll wrap this one in a try/catch as well.
+    // It needs to be in a separate try/catch because if creating theFakeClick
+    // with MouseEvent fails, we still want to fall back to trying with createEvent.
+    if (!theFakeClick && createEvent) {
+      theFakeClick = createEvent('MouseEvent');
+    }
+  } catch (e) {
+    // We'll handle this below as if createEvent doesn't exist.
+  }
+
+  if (!theFakeClick) {
+    // If no method for creating a custom mouse event exists, just use an object.
+    theFakeClick = {};
+  }
+
+  window.MouseEvent = function(type, init) {
+    return theFakeClick;
+  }
+
+  document.createEvent = function(type) {
+    if (type === 'MouseEvent' || type === 'MouseEvents') {
+      return theFakeClick;
+    } else {
+      return createEvent(type);
+    }
   }
 
   $(function() {
@@ -52,11 +67,14 @@
 
       if (!e || !e.originalEvent) {
         isTrusted = false;
-      } else if ('isTrusted' in MouseEvent.prototype) {
+      } else if (MouseEvent instanceof Function &&
+                 'isTrusted' in MouseEvent.prototype) {
         isTrusted = e.originalEvent.isTrusted;
-      } else if (MouseEvent) {
+      } else if (MouseEvent instanceof Function) {
         isTrusted = (e.originalEvent instanceof MouseEvent &&
                      e.originalEvent !== theFakeClick);
+      } else {
+        isTrusted = (e.originalEvent !== theFakeClick);
       }
 
       var voteData = {
@@ -69,5 +87,5 @@
       $.request("vote", voteData);
       $thing.updateThing({ voted: dir });
     });
-  })
+  });
 }(r);