POSIX: Rewrite IPC's interaction with FileDescriptor

chrome/renderer/render_process.cc

Index: chrome/renderer/render_process.cc
diff --git a/chrome/renderer/render_process.cc b/chrome/renderer/render_process.cc
index 80ec5fb61639f115182f00c4a96d52b3b84902ee..8e7c31b1eb9c569aad53b3831a2e424ba11c4f7e 100644
--- a/chrome/renderer/render_process.cc
+++ b/chrome/renderer/render_process.cc
@@ -194,13 +194,13 @@ TransportDIB* RenderProcess::CreateTransportDIB(size_t size) {
 #elif defined(OS_MACOSX)  // defined(OS_WIN) || defined(OS_LINUX)
   // Mac creates transport DIBs in the browser, so we need to do a sync IPC to
   // get one.
-  IPC::Maybe<TransportDIB::Handle> mhandle;
-  IPC::Message* msg = new ViewHostMsg_AllocTransportDIB(size, &mhandle);
+  TransportDIB::Handle handle;
+  IPC::Message* msg = new ViewHostMsg_AllocTransportDIB(size, &handle);
   if (!child_thread()->Send(msg))
     return NULL;
-  if (!mhandle.valid)
+  if (handle.fd < 0)
     return NULL;
-  return TransportDIB::Map(mhandle.value);
+  return TransportDIB::Map(handle);
 #endif  // defined(OS_MACOSX)
 }