1.diff

diff --git a/toolkit/mozapps/extensions/AddonManagerStartup.cpp b/toolkit/mozapps/extensions/AddonManagerStartup.cpp
--- a/toolkit/mozapps/extensions/AddonManagerStartup.cpp
+++ b/toolkit/mozapps/extensions/AddonManagerStartup.cpp
@@ -745,6 +745,16 @@ AddonManagerStartup::Reset()
   return NS_OK;
 }
 
+nsresult
+AddonManagerStartup::InitializeURLPreloader()
+{
+  MOZ_RELEASE_ASSERT(xpc::IsInAutomation());
+
+  URLPreloader::GetSingleton();
+
+  return NS_OK;
+}
+
 /******************************************************************************
  * RegisterChrome
  ******************************************************************************/
diff --git a/toolkit/mozapps/extensions/amIAddonManagerStartup.idl b/toolkit/mozapps/extensions/amIAddonManagerStartup.idl
--- a/toolkit/mozapps/extensions/amIAddonManagerStartup.idl
+++ b/toolkit/mozapps/extensions/amIAddonManagerStartup.idl
@@ -75,4 +75,12 @@ interface amIAddonManagerStartup : nsISu
    * NOT FOR USE OUTSIDE OF UNIT TESTS.
    */
   void reset();
+
+  /**
+   * Initializes the URL Preloader.
+   *
+   * NOT FOR USE OUTSIDE OF UNIT TESTS.
+   */
+  void initializeURLPreloader();
+
 };
diff --git a/toolkit/mozapps/extensions/internal/AddonTestUtils.jsm b/toolkit/mozapps/extensions/internal/AddonTestUtils.jsm
--- a/toolkit/mozapps/extensions/internal/AddonTestUtils.jsm
+++ b/toolkit/mozapps/extensions/internal/AddonTestUtils.jsm
@@ -585,6 +585,12 @@ var AddonTestUtils = {
 
     this.emit("addon-manager-started");
 
+    // We need to set this in order load the URL preloader service, which
+    // is only possible when running in automation.
+    Services.prefs.setBoolPref(PREF_DISABLE_SECURITY, true);
+
+    aomStartup.initializeURLPreloader();
+
     // Load the add-ons list as it was after extension registration
     await this.loadAddonsList(true);
   },