Cleanup: Get rid of OS_WIN/OS_POSIX ifdefs from MojoApplication

ipc/ipc_channel_handle.h

Index: ipc/ipc_channel_handle.h
diff --git a/ipc/ipc_channel_handle.h b/ipc/ipc_channel_handle.h
index 1b6fd8ca2059030d11d07391c3c6ead37e162ede..cdac507f9bbd8bb8cf6fd2524d077e1646c12a79 100644
--- a/ipc/ipc_channel_handle.h
+++ b/ipc/ipc_channel_handle.h
@@ -7,6 +7,7 @@
 
 #include <string>
 
+#include "base/files/platform_file.h"
 #include "build/build_config.h"
 
 #if defined(OS_POSIX)
@@ -51,6 +52,8 @@ struct ChannelHandle {
   std::string name;
 #if defined(OS_POSIX)
   base::FileDescriptor socket;
+
+  base::PlatformFile platform_file() const { return socket.fd; }
 #elif defined(OS_WIN)
   // A simple container to automatically initialize pipe handle
   struct PipeHandle {
@@ -59,6 +62,8 @@ struct ChannelHandle {
     HANDLE handle;
   };
   PipeHandle pipe;
+
+  base::PlatformFile platform_file() const { return pipe.handle; }
 #endif  // defined (OS_WIN)
 };