Work around Webkit bug where sometimes the sizer gets the wrong width

(It'll leave space for a scrollbar to the right of the sizer, though the
scroller does not actually have a scrollbar.)

Issue #2420

Author: marijnh

lib/codemirror.js

@@ -652,6 +652,13 @@
   function setDocumentHeight(cm, measure) {
     cm.display.sizer.style.minHeight = cm.display.heightForcer.style.top = measure.docHeight + "px";
     cm.display.gutters.style.height = Math.max(measure.docHeight, measure.clientHeight - scrollerCutOff) + "px";
+    // Work around Webkit bug where it sometimes reserves space for a
+    // non-existing phantom scrollbar in the scroller (Issue #2420)
+    if (webkit && cm.options.lineWrapping &&
+        cm.display.sizer.offsetWidth + cm.display.gutters.offsetWidth < cm.display.scroller.clientWidth - 1) {
+      cm.display.sizer.style.minHeight = cm.display.heightForcer.style.top = "0px";
+      cm.display.gutters.style.height = measure.docHeight + "px";
+    }
   }
 
   // Read the actual heights of the rendered lines, and update their