sync: reland deferred init

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 055ee49a3a8bac006a3b160f5026735fbc8f1d5c..cfa957b44112677f94fa93ea0017bcfe9adbcce7 100644
--- a/chrome/common/chrome_switches.cc
+++ b/chrome/common/chrome_switches.cc
@@ -1418,7 +1418,11 @@ const char kSyncTrySsltcpFirstForXmpp[]     = "sync-try-ssltcp-first-for-xmpp";
 
 // Enables deferring sync backend initialization until user initiated changes
 // occur.
-const char kSyncEnableDeferredStartup[]     = "sync-enable-deferred-startup";
+const char kSyncDisableDeferredStartup[]     = "sync-disable-deferred-startup";
+
+// Allows overriding the deferred init fallback timeout.
+const char kSyncDeferredStartupTimeoutSeconds[] =
+    "sync-deferred-startup-timeout-seconds";
 
 // Enables feature to avoid unnecessary GetUpdate requests.
 const char kSyncEnableGetUpdateAvoidance[]   =