Bug 827976 - Create the hidden window lazily on non-Mac platforms. r=aklotz

Differential Revision: https://phabricator.services.mozilla.com/D21071

--HG--
extra : moz-landing-system : lando

browser/app/profile/firefox.js

@@ -240,6 +240,10 @@ pref("browser.startup.blankWindow", true);
 pref("browser.startup.blankWindow", false);
 #endif
 
+// Don't create the hidden window during startup on
+// platforms that don't always need it (Win/Linux).
+pref("toolkit.lazyHiddenWindow", true);
+
 pref("browser.slowStartup.notificationDisabled", false);
 pref("browser.slowStartup.timeThreshold", 20000);
 pref("browser.slowStartup.maxSamples", 5);

toolkit/xre/nsAppRunner.cpp

@@ -4610,8 +4610,16 @@ nsresult XREMain::XRE_mainRun() {
   SaveToEnv("XRE_RESTARTED_BY_PROFILE_MANAGER=");
 
   if (!mShuttingDown) {
-    rv = appStartup->CreateHiddenWindow();
-    NS_ENSURE_SUCCESS(rv, NS_ERROR_FAILURE);
+#ifdef XP_MACOSX
+    bool lazyHiddenWindow = false;
+#else
+    bool lazyHiddenWindow = Preferences::GetBool("toolkit.lazyHiddenWindow", false);
+#endif
+
+    if (!lazyHiddenWindow) {
+      rv = appStartup->CreateHiddenWindow();
+      NS_ENSURE_SUCCESS(rv, NS_ERROR_FAILURE);
+    }
 
 #ifdef XP_WIN
     Preferences::RegisterCallbackAndCall(RegisterApplicationRestartChanged,

xpfe/appshell/nsAppShellService.cpp

@@ -91,9 +91,15 @@ nsAppShellService::SetScreenId(uint32_t aScreenId) {
   return NS_OK;
 }
 
+void nsAppShellService::EnsureHiddenWindow() {
+  if (!mHiddenWindow) {
+    CreateHiddenWindowHelper(/* aIsPrivate = */ false);
+  }
+}
+
 void nsAppShellService::EnsurePrivateHiddenWindow() {
   if (!mHiddenPrivateWindow) {
-    CreateHiddenWindowHelper(true);
+    CreateHiddenWindowHelper(/* aIsPrivate = */ true);
   }
 }
 
@@ -719,6 +725,8 @@ NS_IMETHODIMP
 nsAppShellService::GetHiddenWindow(nsIXULWindow** aWindow) {
   NS_ENSURE_ARG_POINTER(aWindow);
 
+  EnsureHiddenWindow();
+
   *aWindow = mHiddenWindow;
   NS_IF_ADDREF(*aWindow);
   return *aWindow ? NS_OK : NS_ERROR_FAILURE;
@@ -726,6 +734,10 @@ nsAppShellService::GetHiddenWindow(nsIXULWindow** aWindow) {
 
 NS_IMETHODIMP
 nsAppShellService::GetHiddenDOMWindow(mozIDOMWindowProxy** aWindow) {
+  NS_ENSURE_ARG_POINTER(aWindow);
+
+  EnsureHiddenWindow();
+
   nsresult rv;
   nsCOMPtr<nsIDocShell> docShell;
   NS_ENSURE_TRUE(mHiddenWindow, NS_ERROR_FAILURE);
@@ -752,6 +764,8 @@ nsAppShellService::GetHiddenPrivateWindow(nsIXULWindow** aWindow) {
 
 NS_IMETHODIMP
 nsAppShellService::GetHiddenPrivateDOMWindow(mozIDOMWindowProxy** aWindow) {
+  NS_ENSURE_ARG_POINTER(aWindow);
+
   EnsurePrivateHiddenWindow();
 
   nsresult rv;
@@ -767,6 +781,14 @@ nsAppShellService::GetHiddenPrivateDOMWindow(mozIDOMWindowProxy** aWindow) {
   return *aWindow ? NS_OK : NS_ERROR_FAILURE;
 }
 
+NS_IMETHODIMP
+nsAppShellService::GetHasHiddenWindow(bool* aHasHiddenWindow) {
+  NS_ENSURE_ARG_POINTER(aHasHiddenWindow);
+
+  *aHasHiddenWindow = !!mHiddenWindow;
+  return NS_OK;
+}
+
 NS_IMETHODIMP
 nsAppShellService::GetHasHiddenPrivateWindow(bool* aHasPrivateWindow) {
   NS_ENSURE_ARG_POINTER(aHasPrivateWindow);

xpfe/appshell/nsAppShellService.h

@@ -36,6 +36,7 @@ class nsAppShellService final : public nsIAppShellService, public nsIObserver {
   ~nsAppShellService();
 
   nsresult CreateHiddenWindowHelper(bool aIsPrivate);
+  void EnsureHiddenWindow();
   void EnsurePrivateHiddenWindow();
 
   nsresult JustCreateTopWindow(nsIXULWindow *aParent, nsIURI *aUrl,

xpfe/appshell/nsIAppShellService.idl

@@ -132,6 +132,11 @@ interface nsIAppShellService : nsISupports
    */
   void unregisterTopLevelWindow(in nsIXULWindow aWindow);
 
+  /**
+   * Whether the hidden window has been lazily created.
+   */
+  readonly attribute boolean hasHiddenWindow;
+
   /**
    * Whether the hidden private window has been lazily created.
    */