Remove support for the obsolete <isindex> tag.

LayoutTests/fast/events/resources/tabindex-focus-blur-all.js

 if (window.testRunner) {
     testRunner.waitUntilDone();
     testRunner.dumpAsText();
 }
 
 var consoleOutput = null;
 var stopTest = false;
 var focusCount = 0;
 var blurCount = 0;
 var focusedElem = null;
 var failedTestCount = 0;
 
 var tagNamesAlwaysFocused = ["A",
                              "AREA",
                              "BUTTON",
                              "IFRAME",
                              "INPUT",
-                             "ISINDEX",
                              "SELECT",
                              "TEXTAREA",
                              "AUDIO",
                              "VIDEO"];
 
 var tagNamesTransferFocused = ["LABEL"]; // labels always transfer focus to the labeled element
 
 var noDisplayTagNamesWithFocus = ["AREA"];  // AREA elements can get focus, but are not displayed.
 
 function printToConsole(str)
@@ skipping 99 matching lines @@
         failedTestCount++;
         printToConsole(elem.id+" FAILED - was " + (focusedElem ? "" : " not ") + " focused but focus " + (elemThatShouldFocus ? " was " : " wasn\'t") + " expected");
         if (elemThatShouldFocus && focusedElem)
             printToConsole("elemThatShouldFocus is <"+elemThatShouldFocus.tagName+"> "+elemThatShouldFocus.id+", focusedElem is <"+focusedElem.tagName+"> "+focusedElem.id);
         if (!elemThatShouldFocus)
             printToConsole("elemThatShouldFocus is null, focusedElem is <"+focusedElem.tagName+"> "+focusedElem.id);
         if (!focusedElem)
             printToConsole("elemThatShouldFocus is <"+elemThatShouldFocus.tagName+"> "+elemThatShouldFocus.id+", focusedElem is null");
     }
 }