Add FilePath to base namespace.

chrome/browser/history/in_memory_history_backend.h

Index: chrome/browser/history/in_memory_history_backend.h
diff --git a/chrome/browser/history/in_memory_history_backend.h b/chrome/browser/history/in_memory_history_backend.h
index addfac95fd2e1a0b6edaef145ffb2480ffa46011..a2d1f721e8d6eec51531f928f4aaadab2b246b20 100644
--- a/chrome/browser/history/in_memory_history_backend.h
+++ b/chrome/browser/history/in_memory_history_backend.h
@@ -21,10 +21,13 @@
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 
-class FilePath;
 class GURL;
 class Profile;
 
+namespace base {
+class FilePath;
+}
+
 namespace history {
 
 class InMemoryDatabase;
@@ -42,7 +45,7 @@ class InMemoryHistoryBackend : public content::NotificationObserver {
   // Initializes the backend from the history database pointed to by the
   // full path in |history_filename|. |db| is used for setting up the
   // InMemoryDatabase.
-  bool Init(const FilePath& history_filename, URLDatabase* db);
+  bool Init(const base::FilePath& history_filename, URLDatabase* db);
 
   // Does initialization work when this object is attached to the history
   // system on the main thread. The argument is the profile with which the