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

base/files/file.cc

Index: base/files/file.cc
diff --git a/base/files/file.cc b/base/files/file.cc
index 4902f15a2ff02744e44699317565797ebf0c05b3..508103ac7d4e1ebac1d376565bd25f3b86abe258 100644
--- a/base/files/file.cc
+++ b/base/files/file.cc
@@ -31,14 +31,17 @@ File::File(const FilePath& name, uint32 flags)
       error_(FILE_OK),
       created_(false),
       async_(false) {
-  if (name.ReferencesParent()) {
-    error_ = FILE_ERROR_ACCESS_DENIED;
-    return;
-  }
-  CreateBaseFileUnsafe(name, flags);
+  Initialize(name, flags);
 }
 #endif
 
+File::File(PlatformFile platform_file)
+    : file_(platform_file),
+      error_(FILE_OK),
+      created_(false),
+      async_(false) {
+}
+
 File::File(RValue other)
     : file_(other.object->TakePlatformFile()),
       error_(other.object->error()),
@@ -61,4 +64,14 @@ File& File::operator=(RValue other) {
   return *this;
 }
 
+#if !defined(OS_NACL)
+void File::Initialize(const FilePath& name, uint32 flags) {
+  if (name.ReferencesParent()) {
+    error_ = FILE_ERROR_ACCESS_DENIED;
+    return;
+  }
+  InitializeUnsafe(name, flags);
+}
+#endif
+
 }  // namespace base