--- a/toolkit/xre/nsAppRunner.cpp
+++ b/toolkit/xre/nsAppRunner.cpp
@@ -36,16 +36,21 @@
  * use your version of this file under the terms of the MPL, indicate your
  * decision by deleting the provisions above and replace them with the notice
  * and other provisions required by the GPL or the LGPL. If you do not delete
  * the provisions above, a recipient may use your version of this file under
  * the terms of any one of the MPL, the GPL or the LGPL.
  *
  * ***** END LICENSE BLOCK ***** */
 
+#ifdef MOZ_IPC
+#include "mozilla/dom/ContentParent.h"
+using mozilla::dom::ContentParent;
+#endif
+
 #if defined(XP_OS2) && defined(MOZ_OS2_HIGH_MEMORY)
 // os2safe.h has to be included before os2.h, needed for high mem
 #include <os2safe.h>
 #endif
 
 #define XPCOM_TRANSLATE_NSGM_ENTRY_POINT 1
 
 #if defined(MOZ_WIDGET_QT)
@@ -759,16 +764,28 @@ NS_IMETHODIMP
 nsXULAppInfo::GetProcessType(PRUint32* aResult)
 {
   NS_ENSURE_ARG_POINTER(aResult);
   *aResult = XRE_GetProcessType();
   return NS_OK;
 }
 
 NS_IMETHODIMP
+nsXULAppInfo::EnsureContentProcess()
+{
+  if (XRE_GetProcessType() != GeckoProcessType_Default)
+    return NS_ERROR_NOT_AVAILABLE;
+
+  ContentParent* c = ContentParent::GetSingleton();
+  if (!c)
+    return NS_ERROR_NOT_AVAILABLE;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
 nsXULAppInfo::InvalidateCachesOnRestart()
 {
   nsCOMPtr<nsIFile> file;
   nsresult rv = NS_GetSpecialDirectory(NS_APP_PROFILE_DIR_STARTUP, 
                                        getter_AddRefs(file));
   if (NS_FAILED(rv))
     return rv;
   if (!file)

--- a/xpcom/system/nsIXULRuntime.idl
+++ b/xpcom/system/nsIXULRuntime.idl
@@ -39,17 +39,17 @@
 
 /**
  * Provides information about the XUL runtime.
  * @status UNSTABLE - This interface is not frozen and will probably change in
  *                    future releases. If you need this functionality to be
  *                    stable/frozen, please contact Benjamin Smedberg.
  */
 
-[scriptable, uuid(cb6078bb-c6b3-4f35-acfd-3b4efa934484)]
+[scriptable, uuid(7685dac8-3637-4660-a544-928c5ec0e714)]
 interface nsIXULRuntime : nsISupports
 {
   /**
    * Whether the application was launched in safe mode.
    */
   readonly attribute boolean inSafeMode;
 
   /**
@@ -102,9 +102,18 @@ interface nsIXULRuntime : nsISupports
   readonly attribute unsigned long processType;
 
   /**
    * Signal the apprunner to invalidate caches on the next restart.
    * This will cause components to be autoregistered and all
    * fastload data to be re-created.
    */
   void invalidateCachesOnRestart();
+
+  /**
+   * Starts a child process. This method is intented to pre-start a
+   * content child process so that when it is actually needed, it is
+   * ready to go.
+   *
+   * @throw NS_ERROR_NOT_AVAILABLE if not available.
+   */
+  void ensureContentProcess();
 };