Base: Move platform_file.* to files/file.*

base/platform_file.h

Index: base/platform_file.h
diff --git a/base/platform_file.h b/base/platform_file.h
index 62b5c352c0f03c6fbc9f537486dc3e5a7975f109..d9a82cbd3f458105e2d421a9520484a9a8450a22 100644
--- a/base/platform_file.h
+++ b/base/platform_file.h
@@ -19,6 +19,11 @@
 
 namespace base {
 
+// ***************************************************************************
+// ***** Don't use anything from this file anymore. It is being removed!
+// ***** Use base/files/base_file.h instead
+// ***************************************************************************
+
 // PLATFORM_FILE_(OPEN|CREATE).* are mutually exclusive. You should specify
 // exactly one of the five (possibly combining with other flags) when opening
 // or creating a file.