Small fixes for Android QuicTransport

Stadia is running QuicTransport on Android via JNI, some small
compilation fixes were required for this.

PiperOrigin-RevId: 374723964
diff --git a/quic/core/http/quic_spdy_stream.cc b/quic/core/http/quic_spdy_stream.cc
index 3e46fd6..6ec48ca 100644
--- a/quic/core/http/quic_spdy_stream.cc
+++ b/quic/core/http/quic_spdy_stream.cc
@@ -434,7 +434,12 @@
   QuicConnection::ScopedPacketFlusher flusher(spdy_session_->connection());
 
   // Write frame header.
+#if !defined(__ANDROID__)
   struct iovec header_iov = {static_cast<void*>(buffer.get()), header_length};
+#else
+  struct iovec header_iov = {static_cast<void*>(buffer.get()),
+                             static_cast<__kernel_size_t>(header_length)};
+#endif
   QuicMemSliceStorage storage(
       &header_iov, 1,
       spdy_session_->connection()->helper()->GetStreamSendBufferAllocator(),