Add a switch to TestRunner to enable/disable mock spell checker

third_party/WebKit/LayoutTests/editing/spelling/script-tests/spelling-hasspellingmarker.js

 description('This tests if internals.hasSpellingMarker works for differnt type of elements. '
     + 'This test succeds when there are four elements having "zz ". '
     + 'However, only the last one should not contatin spelling marker.');
 
 jsTestIsAsync = true;
+if (window.testRunner)
+    testRunner.setMockSpellCheckerEnabled(true);
 
 var testRoot = document.createElement("div");
 document.body.insertBefore(testRoot, document.body.firstChild);
 
 function addContainer(markup)
 {
     var contatiner = document.createElement("div");
     contatiner.innerHTML = markup;
     testRoot.appendChild(contatiner);
 
@@ skipping 33 matching lines @@
         return setTimeout(verifySpellingMarkers(nextTestCase), 0);
 
     if (window.internals)
         testRoot.style.display = "none";
 
     finishJSTest();
 }
 done();
 
 var successfullyParsed = true;