Bug 1472212 - Ensure that tab does not show busy or burst status whenever we navigate to about:home, about:newtab, or about:welcome in a new window. r=Gijs

Now that we have moved some about: pages to the privileged content process,
opening these URLs from a non-privileged content process will trigger SessionStore
to restore the tab state due to a process flip. We will set favicons for these
URLs earlier to avoid flickering and improve perceived performance.

This patch also prevents the spinner whenever a page with a local about: URI
(about:blank and about: pages that resolve to jar:// or file:// URIs) is
loaded from a process that the URI cannot load in (e.g. loading about:newtab
in the web content process), as well as during tab duplication or session
restoration for such local about: URIs.

Before this patch, there were additional frames when opening a new window, causing
browser/base/content/test/performance/browser_windowopen.js to fail. This patch
will reduce the number of frames when opening a new window.

MozReview-Commit-ID: yjj2964KSz

--HG--
extra : rebase_source : b5087686ad3e1c3eb16d0be9a8031b01d14cb6ab
extra : source : cecc2d52e72e7c6e61137a9147735cb07a079d51

browser/base/content/tabbrowser.js

@@ -710,7 +710,7 @@ window._gBrowser = {
   /**
    * Determine if a URI is an about: page pointing to a local resource.
    */
-  _isLocalAboutURI(aURI, aResolvedURI) {
+  isLocalAboutURI(aURI, aResolvedURI) {
     if (!aURI.schemeIs("about")) {
       return false;
     }
@@ -737,6 +737,15 @@ window._gBrowser = {
     }
   },
 
+  /**
+   * Sets an icon for the tab if the URI is defined in FAVICON_DEFAULTS.
+   */
+  setDefaultIcon(aTab, aURI) {
+    if (aURI && aURI.spec in FAVICON_DEFAULTS) {
+      this.setIcon(aTab, FAVICON_DEFAULTS[aURI.spec]);
+    }
+  },
+
   setIcon(aTab, aIconURL = "", aOriginalURL = aIconURL, aLoadingPrincipal = null) {
     let makeString = (url) => url instanceof Ci.nsIURI ? url.spec : url;
 
@@ -2505,9 +2514,7 @@ window._gBrowser = {
 
     // Hack to ensure that the about:newtab, and about:welcome favicon is loaded
     // instantaneously, to avoid flickering and improve perceived performance.
-    if (aURI in FAVICON_DEFAULTS) {
-      this.setIcon(t, FAVICON_DEFAULTS[aURI]);
-    }
+    this.setDefaultIcon(t, aURIObject);
 
     // Dispatch a new tab notification.  We do this once we're
     // entirely done, so that things are in a consistent state
@@ -4816,7 +4823,7 @@ class TabProgressListener {
     // Don't show progress indicators in tabs for about: URIs
     // pointing to local resources.
     if ((aRequest instanceof Ci.nsIChannel) &&
-        gBrowser._isLocalAboutURI(aRequest.originalURI, aRequest.URI)) {
+        gBrowser.isLocalAboutURI(aRequest.originalURI, aRequest.URI)) {
       return false;
     }
 

browser/base/content/test/tabs/browser_isLocalAboutURI.js

@@ -4,7 +4,7 @@
 "use strict";
 
 /**
- * Unit tests for tabbrowser._isLocalAboutURI to make sure it returns the
+ * Unit tests for tabbrowser.isLocalAboutURI to make sure it returns the
  * appropriate values for various URIs as well as optional resolved URI.
  */
 
@@ -12,9 +12,9 @@ add_task(function test_URI() {
   const check = (spec, expect, description) => {
     const URI = Services.io.newURI(spec);
     try {
-      is(gBrowser._isLocalAboutURI(URI), expect, description);
+      is(gBrowser.isLocalAboutURI(URI), expect, description);
     } catch (ex) {
-      ok(false, "_isLocalAboutURI should not throw");
+      ok(false, "isLocalAboutURI should not throw");
     }
   };
   check("https://www.mozilla.org/", false, "https is not about");
@@ -30,7 +30,7 @@ add_task(function test_URI_with_resolved() {
   const check = (spec, resolvedSpec, expect, description) => {
     const URI = Services.io.newURI(spec);
     const resolvedURI = Services.io.newURI(resolvedSpec);
-    is(gBrowser._isLocalAboutURI(URI, resolvedURI), expect, description);
+    is(gBrowser.isLocalAboutURI(URI, resolvedURI), expect, description);
   };
   check("about:newtab",
     "jar:file:///Applications/Firefox.app/Contents/Resources/browser/omni.ja!/chrome/browser/res/activity-stream/prerendered/en-US/activity-stream.html",

browser/components/sessionstore/SessionStore.jsm

@@ -2436,8 +2436,17 @@ var SessionStoreInternal = {
     let newTab = aWindow.gBrowser.addTrustedTab(null, tabOptions);
 
     // Start the throbber to pretend we're doing something while actually
-    // waiting for data from the frame script.
-    newTab.setAttribute("busy", "true");
+    // waiting for data from the frame script. This throbber is disabled
+    // if the URI is a local about: URI.
+    let uriObj = aTab.linkedBrowser.currentURI;
+    if (!uriObj || (uriObj && !aWindow.gBrowser.isLocalAboutURI(uriObj))) {
+      newTab.setAttribute("busy", "true");
+    }
+
+    // Hack to ensure that the about:home, about:newtab, and about:welcome
+    // favicon is loaded instantaneously, to avoid flickering and improve
+    // perceived performance.
+    aWindow.gBrowser.setDefaultIcon(newTab, uriObj);
 
     // Collect state before flushing.
     let tabState = TabState.collect(aTab, TAB_CUSTOM_VALUES.get(aTab));
@@ -2774,7 +2783,14 @@ var SessionStoreInternal = {
 
     // Restore the tab icon.
     if ("image" in tabData) {
-      win.gBrowser.setIcon(tab, tabData.image, undefined, tabData.iconLoadingPrincipal);
+      // We know that about:blank is safe to load in any remote type. Since
+      // SessionStore is triggered with about:blank, there must be a process
+      // flip. We will ignore the first about:blank load to prevent resetting the
+      // favicon that we have set earlier to avoid flickering and improve
+      // perceived performance.
+      if (!activePageData || (activePageData && activePageData.url != "about:blank")) {
+        win.gBrowser.setIcon(tab, tabData.image, undefined, tabData.iconLoadingPrincipal);
+      }
       TabStateCache.update(browser, { image: null, iconLoadingPrincipal: null });
     }
   },
@@ -3014,9 +3030,22 @@ var SessionStoreInternal = {
       return;
     }
 
+    let uriObj;
+    try {
+      uriObj = Services.io.newURI(loadArguments.uri);
+    } catch (e) {}
+
     // Start the throbber to pretend we're doing something while actually
-    // waiting for data from the frame script.
-    tab.setAttribute("busy", "true");
+    // waiting for data from the frame script. This throbber is disabled
+    // if the URI is a local about: URI.
+    if (!uriObj || (uriObj && !window.gBrowser.isLocalAboutURI(uriObj))) {
+      tab.setAttribute("busy", "true");
+    }
+
+    // Hack to ensure that the about:home, about:newtab, and about:welcome
+    // favicon is loaded instantaneously, to avoid flickering and improve
+    // perceived performance.
+    window.gBrowser.setDefaultIcon(tab, uriObj);
 
     // Flush to get the latest tab state.
     TabStateFlusher.flush(browser).then(() => {

browser/modules/AsyncTabSwitcher.jsm

@@ -353,7 +353,7 @@ class AsyncTabSwitcher {
       // determined by the busy state on the tab element and checking
       // if the loaded URI is local.
       let hasSufficientlyLoaded = !this.requestedTab.hasAttribute("busy") &&
-        !this.tabbrowser._isLocalAboutURI(requestedBrowser.currentURI);
+        !this.tabbrowser.isLocalAboutURI(requestedBrowser.currentURI);
 
       let fl = requestedBrowser.frameLoader;
       shouldBeBlank = !this.minimizedOrFullyOccluded &&