Superset of Nacl Keepalive patch & tests - NOT FOR LANDING DIRECTLY.

ppapi/tests/extensions/background_keepalive/background.js

+var NaClModulesExpected = 0;
+var NaClModulesLoaded = 0;
+
+// Indicate load success.
+function moduleDidLoad() {
+  NaClModulesLoaded++;
+  if (NaClModulesLoaded == NaClModulesExpected)
+    chrome.test.sendMessage("nacl_modules_loaded", handleChromeTestMessage);
+}
+
+var handleChromeTestMessage = function (message) {
+  NaClModules = document.querySelectorAll('embed');
+  for (var i = 0; i < NaClModules.length; i++) {
+    NaClModules[i].postMessage(message);
+  }
+}
+
+function handleNaclMessage(message_event) {
+  console.log("handleNaclMessage: " + message_event.data);
+}
+
+function createNaClEmbed() {
+  NaClModulesExpected++;
+
+  var listener = document.createElement("div");
+  listener.addEventListener("load", moduleDidLoad, true);
+  listener.addEventListener("message", handleNaclMessage, true);
+  listener.innerHTML = '<embed' +
+    ' src="ppapi_tests_extensions_background_keepalive.nmf"' +
+    ' type="application/x-nacl" />';
+  document.body.appendChild(listener);
+}
+
+// Create 2 embeds to verify that we can handle more than one.
+createNaClEmbed();
+createNaClEmbed();
+