base: Move MemoryMappedFile out of file_util.h and into its own header file.

media/filters/file_data_source.h

Index: media/filters/file_data_source.h
diff --git a/media/filters/file_data_source.h b/media/filters/file_data_source.h
index edf9e81aeb20c8e93b246804b5eca5d822936467..c4254864b291e49ccec7214a080edfdd50777602 100644
--- a/media/filters/file_data_source.h
+++ b/media/filters/file_data_source.h
@@ -8,7 +8,7 @@
 #include <string>
 
 #include "base/file_path.h"
-#include "base/file_util.h"
+#include "base/files/memory_mapped_file.h"
 #include "media/base/data_source.h"
 
 namespace media {
@@ -41,7 +41,7 @@ class MEDIA_EXPORT FileDataSource : public DataSource {
   // Informs the host of changes in total and buffered bytes.
   void UpdateHostBytes();
 
-  file_util::MemoryMappedFile file_;
+  base::MemoryMappedFile file_;
 
   bool force_read_errors_;
   bool force_streaming_;