Fix highlight being eclipsed by other blocks.

core/block_svg.js

@@ -1413,7 +1413,12 @@ Blockly.BlockSvg.prototype.addSelect = function() {
   Blockly.addClass_(/** @type {!Element} */ (this.svgGroup_),
                     'blocklySelected');
   // Move the selected block to the top of the stack.
-  this.svgGroup_.parentNode.appendChild(this.svgGroup_);
+  var block = this;
+  do {
+    var root = block.getSvgRoot();
+    root.parentNode.appendChild(root);
+    block = block.getParent();
+  } while (block);
 };
 
 /**