Remove all code related to the PreRead field trial.

chrome/app/file_pre_reader_win.h

Index: chrome/app/file_pre_reader_win.h
diff --git a/chrome/app/file_pre_reader_win.h b/chrome/app/file_pre_reader_win.h
index 93cc2e7f8e28f33dc6dc39b3c31e8fb227416eaa..dcd596c1c0c0ec4285ac9137e9a52df017ec31a7 100644
--- a/chrome/app/file_pre_reader_win.h
+++ b/chrome/app/file_pre_reader_win.h
@@ -12,13 +12,8 @@ namespace base {
 class FilePath;
 }
 
-namespace startup_metric_utils {
-struct PreReadOptions;
-}
-
 // Pre-reads |file_path| to avoid touching the disk when the file is actually
-// used. Checks |pre_read_options| to determine how to pre-read the file.
-void PreReadFile(const base::FilePath& file_path,
-                 const startup_metric_utils::PreReadOptions& pre_read_options);
+// used.
+void PreReadFile(const base::FilePath& file_path);
 
 #endif  // CHROME_APP_FILE_PRE_READER_WIN_H_