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..5de034fe434cb7ab69a8a5211459aba6fb14bee2 100644
--- a/chrome/test/data/extensions/api_test/sessions/sessions.js
+++ b/chrome/test/data/extensions/api_test/sessions/sessions.js
@@ -59,6 +59,18 @@ function checkEntries(expectedEntries, actualEntries) {
   });
 }
 
+function checkOnChangedEvent(expectedCallbackCount) {
+  var callbackCount = 0;
+  var doneListening = chrome.test.listenForever(
+    chrome.sessions.onChanged,
+    function() {
+      callbackCount++;
+      if (callbackCount == expectedCallbackCount)
+        doneListening();
+    }
+  );
+}

[not at google - send to devlin, 2014/03/21 10:52:59]

this doesn't actually make any assertions. yes it counts but what then? does it
mean that the test times out? that's not a great experience. what if it's called
too many times?

testing events is hard :\

an alternatively might be to add a listener for each test then do like

assertEq(2, numEventsFired)

or whatever.

[wjywbs, 2014/03/21 19:45:33]

I haven't found a good way yet. I looked at the other api tests just now, such
as chrome.tabs.onRemoved event:
chrome/test/data/extensions/api_test/tabs/on_removed/test.js
In that test, it used chrome.test.listenOnce, so if the callback is called for
multiple times, it would not detect that. Yes, it times out if the listener is
not called.

If we do assertEq(2, numEventsFired), I think I need to wait for 1 or 2 seconds
for finishing the callbacks and then do this check. Is this acceptable?

+
 chrome.test.runTests([
   // After setupWindows
   //
@@ -108,6 +120,8 @@ 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 +148,8 @@ 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 +213,8 @@ chrome.test.runTests([
   },
 
   function restoreClosedTabs() {
+    checkOnChangedEvent(2);
+
     chrome.windows.get(windowIds[0], {"populate": true},
       callbackPass(function(win) {
         var tabCountBeforeRestore = win.tabs.length;
@@ -219,6 +237,8 @@ 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 +257,8 @@ 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 +307,8 @@ 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) {