Selection API: Do not change focus by Selection functions.

third_party/WebKit/LayoutTests/editing/inserting/paragraph-separator-in-table-1.html

 <script>
 if (window.testRunner)
      testRunner.dumpEditingCallbacks();
 </script>
 <p>This tests InsertParagraphSeparator inside table cells.  'Cell' and 'Two' should be on separate lines.</p>
 
 <div contenteditable="true"><table border="1"><tr><td>Cell One</td><td>Cell <span id="test">Two</span></td></tr></table></div>
 
 <script>
 var e = document.getElementById("test").firstChild;
 var s = window.getSelection();
+document.querySelector("div").focus();
 
 s.collapse(e, 0);
 document.execCommand("InsertParagraph");
 </script>