Add an arbitrary delay before unloading lazy background pages.

chrome/common/chrome_switches.cc

Index: chrome/common/chrome_switches.cc
diff --git a/chrome/common/chrome_switches.cc b/chrome/common/chrome_switches.cc
index 54158781922948c804b15f3389277bf7f30f0757..932b2d7f4ba3b734afd18636b26b0ece291ea299 100644
--- a/chrome/common/chrome_switches.cc
+++ b/chrome/common/chrome_switches.cc
@@ -645,6 +645,14 @@ const char kExperimentalSpellcheckerFeatures[] =
 // numbers.
 const char kExplicitlyAllowedPorts[]        = "explicitly-allowed-ports";
 
+// The time in seconds that an extension event page can be idle before it
+// is shut down.
+const char kEventPageIdleTime[]             = "event-page-idle-time";
+
+// The time in seconds that an extension event page has between being notified
+// of its impending unload and that unload happening.
+const char kEventPageUnloadingTime[]        = "event-page-unloading-time";
+
 // Marks a renderer as extension process.
 const char kExtensionProcess[]              = "extension-process";