Bug 1471243 - Do not prerender ActivityStream for about:welcome r=k88hudson

MozReview-Commit-ID: IDyWGnuMndy

--HG--
extra : rebase_source : bd20b556d7680624113696f2caeecf8a6e8bd51e

browser/components/about/AboutRedirector.cpp

@@ -167,8 +167,7 @@ AboutRedirector::NewChannel(nsIURI* aURI,
       // Let the aboutNewTabService decide where to redirect for about:home and
       // enabled about:newtab. Disabledx about:newtab page uses fallback.
       if (path.EqualsLiteral("home") ||
-          (sNewTabPageEnabled && path.EqualsLiteral("newtab")) ||
-          path.EqualsLiteral("welcome")) {
+          (sNewTabPageEnabled && path.EqualsLiteral("newtab"))) {
         nsCOMPtr<nsIAboutNewTabService> aboutNewTabService =
           do_GetService("@mozilla.org/browser/aboutnewtab-service;1", &rv);
         NS_ENSURE_SUCCESS(rv, rv);
@@ -176,6 +175,14 @@ AboutRedirector::NewChannel(nsIURI* aURI,
         NS_ENSURE_SUCCESS(rv, rv);
       }
 
+      if (path.EqualsLiteral("welcome")) {
+        nsCOMPtr<nsIAboutNewTabService> aboutNewTabService =
+          do_GetService("@mozilla.org/browser/aboutnewtab-service;1", &rv);
+        NS_ENSURE_SUCCESS(rv, rv);
+        rv = aboutNewTabService->GetWelcomeURL(url);
+        NS_ENSURE_SUCCESS(rv, rv);
+      }
+
       if (sNewCertErrorPageEnabled && path.EqualsLiteral("certerror")) {
         url.AssignASCII("chrome://browser/content/aboutNetError-new.xhtml");
       }

browser/components/newtab/aboutNewTabService.js

@@ -258,6 +258,20 @@ AboutNewTabService.prototype = {
     ].join("");
   },
 
+  /*
+   * Returns the about:welcome URL
+   *
+   * This is calculated in the same way the default URL is, except that we don't
+   * allow prerendering.
+   */
+  get welcomeURL() {
+    const prerenderEnabled = this._activityStreamPrerender;
+    this._activityStreamPrerender = false;
+    const url = this.defaultURL;
+    this._activityStreamPrerender = prerenderEnabled;
+    return url;
+  },
+
   get newTabURL() {
     return this._newTabURL;
   },

browser/components/newtab/nsIAboutNewTabService.idl

@@ -23,6 +23,11 @@ interface nsIAboutNewTabService : nsISupports
    */
   attribute ACString defaultURL;
 
+  /**
+   * Returns the about:welcome URL.
+   */
+  attribute ACString welcomeURL;
+
   /**
    * Returns true if opening the New Tab page will notify the user of a change.
    */

browser/components/newtab/tests/xpcshell/test_AboutNewTabService.js

@@ -129,6 +129,33 @@ add_task(async function test_default_url() {
   cleanup();
 });
 
+add_task(async function test_welcome_url() {
+  await setupASPrerendered();
+
+  Assert.equal(aboutNewTabService.activityStreamPrerender, true,
+    "Prerendering is enabled by default.");
+  Assert.equal(aboutNewTabService.welcomeURL, ACTIVITY_STREAM_URL,
+    "Newtab welcomeURL set to un-prerendered AS when prerendering enabled and debug disabled.");
+  await setBoolPrefAndWaitForChange(ACTIVITY_STREAM_PRERENDER_PREF, false,
+    "A notification occurs after changing the prerender pref to false.");
+  Assert.equal(aboutNewTabService.welcomeURL, aboutNewTabService.defaultURL,
+    "Newtab welcomeURL is equal to defaultURL when prerendering disabled and debug disabled.");
+
+  // Only debug variants aren't available on release/beta
+  if (!IS_RELEASE_OR_BETA) {
+    await setBoolPrefAndWaitForChange(ACTIVITY_STREAM_DEBUG_PREF, true,
+      "A notification occurs after changing the debug pref to true.");
+    Assert.equal(aboutNewTabService.welcomeURL, aboutNewTabService.welcomeURL,
+      "Newtab welcomeURL is equal to defaultURL when prerendering disabled and debug enabled.");
+    await setBoolPrefAndWaitForChange(ACTIVITY_STREAM_PRERENDER_PREF, true,
+      "A notification occurs after changing the prerender pref to true.");
+    Assert.equal(aboutNewTabService.welcomeURL, ACTIVITY_STREAM_DEBUG_URL,
+      "Newtab welcomeURL set to un-prerendered debug AS when prerendering enabled and debug enabled");
+  }
+
+  cleanup();
+});
+
 add_task(function test_locale() {
   Assert.equal(aboutNewTabService.activityStreamLocale, "en-US",
     "The locale for testing should be en-US");