AAPT2: Better debugging output

Test: make aapt2_tests
Change-Id: I7778b773201381538dc1f2e376abee4eb33e44c0
diff --git a/tools/aapt2/io/Util.h b/tools/aapt2/io/Util.h
index 1e48508..de2ab39 100644
--- a/tools/aapt2/io/Util.h
+++ b/tools/aapt2/io/Util.h
@@ -42,6 +42,7 @@
 // Copies the data from in to out. Returns false if there was an error.
 // If there was an error, check the individual streams' HadError/GetError methods.
 bool Copy(OutputStream* out, InputStream* in);
+bool Copy(OutputStream* out, const ::android::StringPiece& in);
 bool Copy(::google::protobuf::io::ZeroCopyOutputStream* out, InputStream* in);
 
 class OutputStreamAdaptor : public io::OutputStream {