Revert "FBTF: Move the TabRestoreService::Observer into its own file."

chrome/browser/sessions/session_backend.h

Index: chrome/browser/sessions/session_backend.h
diff --git a/chrome/browser/sessions/session_backend.h b/chrome/browser/sessions/session_backend.h
index 883a58f4c0e315e197450ad507b5ae4d43bac1ff..523ef58b7b0a124e4b50ba40b6a4b77a74347c13 100644
--- a/chrome/browser/sessions/session_backend.h
+++ b/chrome/browser/sessions/session_backend.h
@@ -12,10 +12,7 @@
 #include "base/scoped_ptr.h"
 #include "chrome/browser/sessions/base_session_service.h"
 #include "chrome/browser/sessions/session_command.h"
-
-namespace net {
-class FileStream;
-}
+#include "net/base/file_stream.h"
 
 // SessionBackend -------------------------------------------------------------
 
@@ -96,7 +93,7 @@ class SessionBackend : public base::RefCountedThreadSafe<SessionBackend> {
  private:
   friend class base::RefCountedThreadSafe<SessionBackend>;
 
-  ~SessionBackend();
+  ~SessionBackend() {}
 
   // If current_session_file_ is open, it is truncated so that it is essentially
   // empty (only contains the header). If current_session_file_ isn't open, it