Refactor shutdown code to allow win/linux to run after last browser closes.

chrome/browser/profile_manager.cc

Index: chrome/browser/profile_manager.cc
diff --git a/chrome/browser/profile_manager.cc b/chrome/browser/profile_manager.cc
index 1e948a31708230cca73e6ef972c5d0a291f11ee6..8770b1dffa55cf0f937b51044bbc754f586a54e9 100644
--- a/chrome/browser/profile_manager.cc
+++ b/chrome/browser/profile_manager.cc
@@ -39,6 +39,8 @@
 // static
 void ProfileManager::ShutdownSessionServices() {
   ProfileManager* pm = g_browser_process->profile_manager();
+  if (!pm) // Is NULL when running unit tests.
+    return;
   for (ProfileManager::const_iterator i = pm->begin(); i != pm->end(); ++i)
     (*i)->ShutdownSessionService();
 }