Convert base::MemoryMappedFile to use File instead of PlatformFile.

media/base/media_file_checker.cc

Index: media/base/media_file_checker.cc
diff --git a/media/base/media_file_checker.cc b/media/base/media_file_checker.cc
index 494657d209f1917b28dadf9c0f7da26dbbb0d53b..74e83b65784c4811d3249f753fbfba123ad0e732 100644
--- a/media/base/media_file_checker.cc
+++ b/media/base/media_file_checker.cc
@@ -21,20 +21,17 @@ static void OnError(bool* called) {
   *called = false;
 }
 
-MediaFileChecker::MediaFileChecker(const base::PlatformFile& file)
-    : file_(file),
-      file_closer_(&file_) {
+MediaFileChecker::MediaFileChecker(base::File file) : file_(file.Pass()) {
 }
 
 MediaFileChecker::~MediaFileChecker() {
 }
 
 bool MediaFileChecker::Start(base::TimeDelta check_time) {
-  media::FileDataSource source;
+  media::FileDataSource source(file_.Pass());
   bool read_ok = true;
   media::BlockingUrlProtocol protocol(&source, base::Bind(&OnError, &read_ok));
   media::FFmpegGlue glue(&protocol);
-  source.InitializeFromPlatformFile(file_);
   AVFormatContext* format_context = glue.format_context();
 
   if (!glue.OpenContext())