Add POSIX shared memory support for Mac

mojo/edk/embedder/platform_shared_buffer_unittest.cc

Index: mojo/edk/embedder/platform_shared_buffer_unittest.cc
diff --git a/mojo/edk/embedder/platform_shared_buffer_unittest.cc b/mojo/edk/embedder/platform_shared_buffer_unittest.cc
index f1593f06c448f7ceec3d12d7d44b196659149cd4..9b56ae2d19f31373761d88fcf87a08f9c8cef5fc 100644
--- a/mojo/edk/embedder/platform_shared_buffer_unittest.cc
+++ b/mojo/edk/embedder/platform_shared_buffer_unittest.cc
@@ -196,6 +196,9 @@ TEST(PlatformSharedBufferTest, FromSharedMemoryHandle) {
   const size_t kBufferSize = 1234;
   base::SharedMemoryCreateOptions options;
   options.size = kBufferSize;
+#if defined(OS_MACOSX) && !defined(OS_IOS)
+  options.type = base::SharedMemoryHandle::POSIX;
+#endif
   base::SharedMemory shared_memory;
   ASSERT_TRUE(shared_memory.Create(options));
   ASSERT_TRUE(shared_memory.Map(kBufferSize));