Eliminate FilePathWatcher::Delegate.

base/files/file_path_watcher_stub.cc

Index: base/files/file_path_watcher_stub.cc
diff --git a/base/files/file_path_watcher_stub.cc b/base/files/file_path_watcher_stub.cc
index 0c25d7f86f8651ab04e0a0244c9555014afb99dd..fc3001f468ccf6542d9da4f2f42bd9e6468201bb 100644
--- a/base/files/file_path_watcher_stub.cc
+++ b/base/files/file_path_watcher_stub.cc
@@ -16,7 +16,7 @@ class FilePathWatcherImpl : public FilePathWatcher::PlatformDelegate {
  public:
   virtual bool Watch(const FilePath& path,
                      bool recursive,
-                     FilePathWatcher::Delegate* delegate) OVERRIDE {
+                     const FilePathWatcher::Callback& callback) OVERRIDE {
     return false;
   }