Add POSIX shared memory support for Mac

mojo/edk/embedder/platform_shared_buffer.cc

Index: mojo/edk/embedder/platform_shared_buffer.cc
diff --git a/mojo/edk/embedder/platform_shared_buffer.cc b/mojo/edk/embedder/platform_shared_buffer.cc
index 58af44df8f8c2763ce50a135c01b744e62fdd844..02b5b07b4c103e78cae571db7c3e0ee2774cb0be 100644
--- a/mojo/edk/embedder/platform_shared_buffer.cc
+++ b/mojo/edk/embedder/platform_shared_buffer.cc
@@ -33,7 +33,14 @@ ScopedPlatformHandle SharedMemoryToPlatformHandle(
 #elif defined(OS_WIN)
   return ScopedPlatformHandle(PlatformHandle(memory_handle.GetHandle()));
 #else
-  return ScopedPlatformHandle(PlatformHandle(memory_handle.GetMemoryObject()));
+  if (memory_handle.GetType() == base::SharedMemoryHandle::MACH) {
+    return ScopedPlatformHandle(PlatformHandle(
+        memory_handle.GetMemoryObject()));
+  } else {
+    // We should never pass POSIX shared memory over IPC.
+    CHECK(false);
+    return ScopedPlatformHandle();
+  }
 #endif
 }
 
@@ -226,6 +233,9 @@ bool PlatformSharedBuffer::Init() {
   options.size = num_bytes_;
   // By default, we can share as read-only.
   options.share_read_only = true;
+#if defined(OS_MACOSX) && !defined(OS_IOS)
+  options.type = base::SharedMemoryHandle::MACH;
+#endif
 
   shared_memory_.reset(new base::SharedMemory);
   return shared_memory_->Create(options);
@@ -240,8 +250,12 @@ bool PlatformSharedBuffer::InitFromPlatformHandle(
                                   base::GetCurrentProcId());
 #elif defined(OS_MACOSX) && !defined(OS_IOS)
   base::SharedMemoryHandle handle;
-  handle = base::SharedMemoryHandle(platform_handle.release().port, num_bytes_,
-                                    base::GetCurrentProcId());
+  if (platform_handle.get().type == PlatformHandle::Type::MACH) {
+    handle = base::SharedMemoryHandle(
+        platform_handle.release().port, num_bytes_, base::GetCurrentProcId());
+  } else {
+    handle = base::SharedMemoryHandle(platform_handle.release().handle, false);
+  }
 #else
   base::SharedMemoryHandle handle(platform_handle.release().handle, false);
 #endif