ART: Replace ScopedFd with FdFile

FdFile can now be used like ScopedFd. Remove ScopedFd.

Bug: 21192156
Test: m test-art-host
Test: m test-art-target (shamu)
Change-Id: I32115fa8b2b8bb5aa5d1886eae63522f80ce836b
diff --git a/runtime/base/file_magic.h b/runtime/base/file_magic.h
index f7e4bad..4b5d2f5 100644
--- a/runtime/base/file_magic.h
+++ b/runtime/base/file_magic.h
@@ -20,12 +20,12 @@
 #include <stdint.h>
 #include <string>
 
-#include "ScopedFd.h"
+#include "os.h"
 
 namespace art {
 
 // Open file and read magic number
-ScopedFd OpenAndReadMagic(const char* filename, uint32_t* magic, std::string* error_msg);
+File OpenAndReadMagic(const char* filename, uint32_t* magic, std::string* error_msg);
 
 // Check whether the given magic matches a known file type.
 bool IsZipMagic(uint32_t magic);