libbinder: Fix FD handling for queued oneway RPC transactions

If a oneway transaction contained FDs and got queued, we'd drop the FDs
and then the Parcel validation would fail with an error once the
transaction was eventually processed.

Bug: 244484370
Test: m libbinder binderRpcTest && out/host/linux-x86/nativetest64/binderRpcTest/binderRpcTest
Change-Id: I781d851d875d496c8b57e3512f3f89c9911e9f3c
diff --git a/libs/binder/tests/IBinderRpcTest.aidl b/libs/binder/tests/IBinderRpcTest.aidl
index b15a225..a3ed571 100644
--- a/libs/binder/tests/IBinderRpcTest.aidl
+++ b/libs/binder/tests/IBinderRpcTest.aidl
@@ -71,4 +71,13 @@
     ParcelFileDescriptor echoAsFile(@utf8InCpp String content);
 
     ParcelFileDescriptor concatFiles(in List<ParcelFileDescriptor> files);
+
+    // FDs sent via `blockingSendFdOneway` can be received via
+    // `blockingRecvFd`. The handler for `blockingSendFdOneway` will block
+    // until the next `blockingRecvFd` call.
+    //
+    // This is useful for carefully controlling how/when oneway transactions
+    // get queued.
+    oneway void blockingSendFdOneway(in ParcelFileDescriptor fd);
+    ParcelFileDescriptor blockingRecvFd();
 }