Move PageTransition into content namespace. While I'm touching all these files, I've also updated...

chrome/browser/sync/glue/synced_session_tracker_unittest.cc

Index: chrome/browser/sync/glue/synced_session_tracker_unittest.cc
===================================================================
--- chrome/browser/sync/glue/synced_session_tracker_unittest.cc	(revision 105162)
+++ chrome/browser/sync/glue/synced_session_tracker_unittest.cc	(working copy)
@@ -64,7 +64,7 @@
   tab->navigations.push_back(TabNavigation(
       0, GURL("valid_url"), GURL("referrer"),
       string16(ASCIIToUTF16("title")),
-      std::string("state"), 0U));
+      std::string("state"), content::PageTransitionFromInt(0)));
   ASSERT_TRUE(tracker.LookupAllForeignSessions(&sessions));
   // Only the session with a valid window and tab gets returned.
   ASSERT_EQ(1U, sessions.size());