Changing SessionService to have a BaseSessionService, not being one.

chrome/browser/sessions/session_service_utils.h

Index: chrome/browser/sessions/session_service_utils.h
diff --git a/chrome/browser/sessions/session_service_utils.h b/chrome/browser/sessions/session_service_utils.h
index 2fdcba05a9ba32b779a47a441fe51b15ecfe8414..38825c7896000ab1e1f6cb4c100322762598012a 100644
--- a/chrome/browser/sessions/session_service_utils.h
+++ b/chrome/browser/sessions/session_service_utils.h
@@ -8,6 +8,10 @@
 #include "chrome/browser/sessions/session_types.h"
 #include "chrome/browser/ui/browser.h"
 
+// The maximum number of navigation entries in each direction we'll persist for
+// chrome/Browser.
+extern const int gMaxPersistNavigationCount;
+
 // Convert back/forward between the Browser and SessionService window types.
 SessionWindow::WindowType WindowTypeForBrowserType(Browser::Type type);
 Browser::Type BrowserTypeForWindowType(SessionWindow::WindowType type);