Cleanup: Get rid of OS_WIN/OS_POSIX ifdefs from MojoApplication

mojo/embedder/platform_handle.h

Index: mojo/embedder/platform_handle.h
diff --git a/mojo/embedder/platform_handle.h b/mojo/embedder/platform_handle.h
index 39da4a9624965abbffd83e19685544e9bcc2c218..cd9b77aed0b7b6c912b49694a6402cebe96742d7 100644
--- a/mojo/embedder/platform_handle.h
+++ b/mojo/embedder/platform_handle.h
@@ -5,6 +5,7 @@
 #ifndef MOJO_EMBEDDER_PLATFORM_HANDLE_H_
 #define MOJO_EMBEDDER_PLATFORM_HANDLE_H_
 
+#include "base/files/platform_file.h"
 #include "build/build_config.h"
 #include "mojo/system/system_impl_export.h"
 
@@ -23,6 +24,7 @@ struct MOJO_SYSTEM_IMPL_EXPORT PlatformHandle {
   void CloseIfNecessary();
 
   bool is_valid() const { return fd != -1; }
+  base::PlatformFile platform_file() const { return fd; }
 
   int fd;
 };
@@ -34,6 +36,7 @@ struct MOJO_SYSTEM_IMPL_EXPORT PlatformHandle {
   void CloseIfNecessary();
 
   bool is_valid() const { return handle != INVALID_HANDLE_VALUE; }
+  base::PlatformFile platform_file() const { return handle; }
 
   HANDLE handle;
 };