Move BufferHubMetadata off pdx::fileHandle

Use android::base::unique_fd to replace LocalHandle. For BorrowedHandle,
a const reference of the unique_fd is returned.

Updated the test cases to fit in current behavior.

Test: BufferHubMetadata_test, BufferHubBuffer_test, BufferNode_test,
buffer_hub-test (passed)
Fix: 118888072

Change-Id: I34de335ed9a10864ac226cd4d7d261ba0078045d
diff --git a/services/vr/bufferhubd/buffer_channel.cpp b/services/vr/bufferhubd/buffer_channel.cpp
index 589b31a..6c64bcd 100644
--- a/services/vr/bufferhubd/buffer_channel.cpp
+++ b/services/vr/bufferhubd/buffer_channel.cpp
@@ -83,10 +83,13 @@
   ATRACE_NAME("BufferChannel::OnImport");
   ALOGD_IF(TRACE, "BufferChannel::OnImport: buffer=%d.", buffer_id());
 
+  BorrowedHandle ashmem_handle =
+      BorrowedHandle(buffer_node_->metadata().ashmem_fd().get());
+
   // TODO(b/112057680) Move away from the GraphicBuffer-based IonBuffer.
   return BufferTraits<BorrowedHandle>{
       /*buffer_handle=*/buffer_node_->buffer_handle(),
-      /*metadata_handle=*/buffer_node_->metadata().ashmem_handle().Borrow(),
+      /*metadata_handle=*/ashmem_handle,
       /*id=*/buffer_id(),
       /*client_state_mask=*/client_state_mask_,
       /*metadata_size=*/buffer_node_->metadata().metadata_size(),