Resurrect POSIX shared memory support on mac

components/nacl/loader/nacl_ipc_adapter.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/nacl/loader/nacl_ipc_adapter.h"
 
 #include <limits.h>
 #include <string.h>
 
 #include <memory>
@@ skipping 216 matching lines @@
 
  private:
   NaClDesc* desc_;
   DISALLOW_COPY_AND_ASSIGN(NaClDescWrapper);
 };
 
 std::unique_ptr<NaClDescWrapper> MakeShmNaClDesc(
     const base::SharedMemoryHandle& handle,
     size_t size) {
 #if defined(OS_MACOSX)
-  return std::unique_ptr<NaClDescWrapper>(new NaClDescWrapper(
-      NaClDescImcShmMachMake(handle.GetMemoryObject(), size)));
+  if (handle.GetType() == base::SharedMemoryHandle::MACH) {
+    return std::unique_ptr<NaClDescWrapper>(new NaClDescWrapper(
+        NaClDescImcShmMachMake(handle.GetMemoryObject(), size)));
+  } else {
+    CHECK_EQ(base::SharedMemoryHandle::POSIX, handle.GetType());
+    return nullptr;
+  }
 #else
   return std::unique_ptr<NaClDescWrapper>(
       new NaClDescWrapper(NaClDescImcShmMake(
 #if defined(OS_WIN)
           handle.GetHandle(),
 #else
           base::SharedMemory::GetFdFromSharedMemoryHandle(handle),
 #endif
           size)));
 #endif
@@ skipping 592 matching lines @@
   header.flags = msg.flags();
   header.num_fds = static_cast<uint16_t>(rewritten_msg->desc_count());
 
   rewritten_msg->SetData(header, msg.payload(), msg.payload_size());
   locked_data_.to_be_received_.push(rewritten_msg);
 }
 
 int TranslatePepperFileReadWriteOpenFlagsForTesting(int32_t pp_open_flags) {
   return TranslatePepperFileReadWriteOpenFlags(pp_open_flags);
 }