Deflake and add more prerender_browsertests focused on back navigation.

chrome/test/data/prerender/prerender_loader.html

Index: chrome/test/data/prerender/prerender_loader.html
===================================================================
--- chrome/test/data/prerender/prerender_loader.html	(revision 98079)
+++ chrome/test/data/prerender/prerender_loader.html	(working copy)
@@ -3,21 +3,66 @@
 <title>Preloader</title>
 
 <script>
-  function ClickOpenLinkInNewWindow() {
+  function Click() {
     var eventObject = document.createEvent('MouseEvents');
     eventObject.initMouseEvent('click');
+    document.getElementById('toClick').dispatchEvent(eventObject);
+    return true;
+  }
+
+  function ClickTarget() {
+    var eventObject = document.createEvent('MouseEvents');
+    eventObject.initMouseEvent('click');
     document.getElementById('toClickTarget').dispatchEvent(eventObject);
     return true;
   }
 
-  function ClickOpenLink() {
+  function ShiftClick() {
     var eventObject = document.createEvent('MouseEvents');
-    eventObject.initMouseEvent('click');
+    eventObject.initMouseEvent('click', true, true, window, 
+                               1, 0, 0, 0, 0, 
+                               false, false, true, false, 0, null);
     document.getElementById('toClick').dispatchEvent(eventObject);
     return true;
   }
 
-  function JsOpenLinkInNewWindow() {
+  function CtrlClick() {
+    var eventObject = document.createEvent('MouseEvents');
+    eventObject.initMouseEvent('click', true, true, window, 
+                               1, 0, 0, 0, 0, 
+                               true, false, false, false, 0, null);
+    document.getElementById('toClick').dispatchEvent(eventObject);
+    return true;
+  }
+
+  function CtrlShiftClick() {
+    var eventObject = document.createEvent('MouseEvents');
+    eventObject.initMouseEvent('click', true, true, window, 
+                               1, 0, 0, 0, 0, 
+                               true, false, true, false, 0, null);
+    document.getElementById('toClick').dispatchEvent(eventObject);
+    return true;
+  }
+
+  function MetaClick() {
+    var eventObject = document.createEvent('MouseEvents');
+    eventObject.initMouseEvent('click', true, true, window, 
+                               1, 0, 0, 0, 0, 
+                               false, false, false, true, 0, null);
+    document.getElementById('toClick').dispatchEvent(eventObject);
+    return true;
+  }
+
+  function MetaShiftClick() {
+    var eventObject = document.createEvent('MouseEvents');
+    eventObject.initMouseEvent('click', true, true, window, 
+                               1, 0, 0, 0, 0, 
+                               false, false, true, true, 0, null);
+    document.getElementById('toClick').dispatchEvent(eventObject);
+    return true;
+  }
+
+  function WindowOpen() {
     window.open('REPLACE_WITH_PRERENDER_URL');
     return true;
   }