Add onChanged callback for chrome.sessions API.

chrome/test/data/extensions/api_test/sessions/sessions.js

Index: chrome/test/data/extensions/api_test/sessions/sessions.js
diff --git a/chrome/test/data/extensions/api_test/sessions/sessions.js b/chrome/test/data/extensions/api_test/sessions/sessions.js
index 431edbec72fb11ed0a052bebb3a721a68cc1e13f..4ad6f504aa43f98542e3fd18a28237684f381da3 100644
--- a/chrome/test/data/extensions/api_test/sessions/sessions.js
+++ b/chrome/test/data/extensions/api_test/sessions/sessions.js
@@ -59,6 +59,26 @@ function checkEntries(expectedEntries, actualEntries) {
   });
 }
 
+function checkOnChangedEvent(expectedCallbackCount) {
+  var callbackCount = 0;
+  var doneListening = chrome.test.listenForever(
+    chrome.sessions.onChanged,

[not at google - send to devlin, 2014/03/26 21:12:38]

I keep reading this as a function body, because the indent is 2 not 4. I suggest
changing this to look like

var done = chrome.test.listenForever(chrome.sessions.onChanged, function() {
  callbackCount++;
});

+    function() {
+      callbackCount++;
+    }
+  );
+
+  var checkEvent = function() {
+    if (callbackCount < expectedCallbackCount)
+      window.setTimeout(checkEvent, 100);
+    else {
+      assertEq(callbackCount, expectedCallbackCount);
+      doneListening();
+    }
+  };
+  window.setTimeout(checkEvent, 1000);

[not at google - send to devlin, 2014/03/26 21:12:38]

It would be nice to notify the user why this test is still alive, if it is. E.g.
log each time the check is re-retried. Really this should be a helper exposed on
chrome.test, like chrome.test.listenNTimes, but let's worry about that later
(perhaps file a bug).

Anyway, it's not just as simple as logging "checking" each time you check,
because that will cause a lot of log spew. There needs to be a way to signal to
the event checker that all the events should have happened by now, and to wait.

How about:
- change the test retry to 1000 (from 100)
- make this function return a function meaning "test is finished, call me now"
- when that function is called, start logging "waiting for <n> more onChanged
events"

+}
+
 chrome.test.runTests([
   // After setupWindows
   //
@@ -108,6 +128,8 @@ chrome.test.runTests([
   function retrieveClosedTabs() {
     // Check that the recently closed list contains what we expect
     // after removing tabs.
+    checkOnChangedEvent(2);
+
     callForEach(
       chrome.tabs.remove,
       firstWindowTabIds.slice(0, 2).reverse(),
@@ -134,6 +156,8 @@ chrome.test.runTests([
   function retrieveClosedWindows() {
     // Check that the recently closed list contains what we expect
     // after removing windows.
+    checkOnChangedEvent(2);
+
     callForEach(
       chrome.windows.remove,
       windowIds.slice(1, 3).reverse(),
@@ -197,6 +221,8 @@ chrome.test.runTests([
   },
 
   function restoreClosedTabs() {
+    checkOnChangedEvent(2);
+
     chrome.windows.get(windowIds[0], {"populate": true},
       callbackPass(function(win) {
         var tabCountBeforeRestore = win.tabs.length;
@@ -219,6 +245,8 @@ chrome.test.runTests([
   },
 
   function restoreTabInClosedWindow() {
+    checkOnChangedEvent(1);
+
     chrome.windows.getAll({"populate": true}, callbackPass(function(win) {
       var windowCountBeforeRestore = win.length;
       chrome.sessions.restore(recentlyClosedSecondWindowTabIds[0],
@@ -237,6 +265,8 @@ chrome.test.runTests([
   },
 
   function restoreClosedWindows() {
+    checkOnChangedEvent(1);
+
     chrome.windows.getAll({"populate": true}, callbackPass(function(win) {
       var windowCountBeforeRestore = win.length;
       chrome.sessions.restore(recentlyClosedWindowIds[0],
@@ -285,6 +315,8 @@ chrome.test.runTests([
   },
 
   function restoreMostRecentEntry() {
+    checkOnChangedEvent(1);
+
     chrome.windows.getAll({"populate": true}, callbackPass(function(win) {
       var windowCountBeforeRestore = win.length;
       chrome.sessions.restore(callbackPass(function(win_session) {