bgTokenizer worker should not redraw unnecessarily

lib/ace/background_tokenizer.js

@@ -68,29 +68,37 @@ var BackgroundTokenizer = function(tokenizer, editor) {
         if (!self.running) { return; }
 
         var workerStart = new Date();
-        var startLine = self.currentLine;
+        var currentLine = self.currentLine;
+        var endLine = -1;
         var doc = self.doc;
 
-        var processedLines = 0;
+        while (self.lines[currentLine])
+            currentLine++;
+
+        var startLine = currentLine;
 
         var len = doc.getLength();
-        while (self.currentLine < len) {
+        var processedLines = 0;
-            self.$tokenizeRow(self.currentLine);
+        self.running = false;
-            while (self.lines[self.currentLine])
+        while (currentLine < len) {
-                self.currentLine++;
+            self.$tokenizeRow(currentLine);
+            endLine = currentLine;
+            do {
+                currentLine++;
+            } while (self.lines[currentLine]);
 
             // only check every 5 lines
             processedLines ++;
-            if ((processedLines % 5 == 0) && (new Date() - workerStart) > 20) {
+            if ((processedLines % 5 == 0) && (new Date() - workerStart) > 20) {                
-                self.fireUpdateEvent(startLine, self.currentLine-1);
                 self.running = setTimeout(self.$worker, 20);
+                self.currentLine = currentLine;
                 return;
             }
         }
-
+        self.currentLine = currentLine;
-        self.running = false;
+        
-
+        if (startLine <= endLine)
-        self.fireUpdateEvent(startLine, len - 1);
+            self.fireUpdateEvent(startLine, endLine);
     };
 };