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

base/files/file_win.cc

Index: base/files/file_win.cc
diff --git a/base/files/file_win.cc b/base/files/file_win.cc
index 94f4d7f59c9431b073619ec71b37a1de780799fe..fab7a393ab01eb411b8d6720e65df8d64b582e93 100644
--- a/base/files/file_win.cc
+++ b/base/files/file_win.cc
@@ -13,7 +13,7 @@
 
 namespace base {
 
-void File::CreateBaseFileUnsafe(const FilePath& name, uint32 flags) {
+void File::InitializeUnsafe(const FilePath& name, uint32 flags) {
   base::ThreadRestrictions::AssertIOAllowed();
   DCHECK(!IsValid());
 
@@ -197,7 +197,17 @@ int File::WriteAtCurrentPosNoBestEffort(const char* data, int size) {
   return WriteAtCurrentPos(data, size);
 }
 
-bool File::Truncate(int64 length) {
+int64 File::GetLength() {
+  base::ThreadRestrictions::AssertIOAllowed();
+  DCHECK(IsValid());
+  LARGE_INTEGER size;
+  if (!::GetFileSizeEx(file_.Get(), &size))
+    return -1;
+
+  return static_cast<int64>(size.QuadPart);
+}
+
+bool File::SetLength(int64 length) {
   base::ThreadRestrictions::AssertIOAllowed();
   DCHECK(IsValid());