Check, after updating display, if viewport is really filled

Due to changed line heights, the rendered content might not reach to
the viewport bottom.

Issue #1147

Author: marijnh

lib/codemirror.js

@@ -503,6 +503,9 @@ window.CodeMirror = (function() {
     display.viewOffset = heightAtLine(cm, getLine(doc, from));
     // Position the mover div to align with the current virtual scroll position
     display.mover.style.top = display.viewOffset + "px";
+
+    if (visibleLines(display, doc, viewPort).to >= to)
+      updateDisplayInner(cm, [], viewPort);
     return true;
   }