Set use_async_processing in windows symupload.

Change-Id: If9cc629a44b8c05e4be55d765800c239c47e076c
Reviewed-on: https://chromium-review.googlesource.com/c/breakpad/breakpad/+/3554917
Reviewed-by: Ivan Penkov <ivanpe@chromium.org>

src/common/windows/symbol_collector_client.cc

@@ -78,7 +78,8 @@ namespace google_breakpad {
         L"{ symbol_id: {"
         L"debug_file: \"" + debug_file + L"\", "
         L"debug_id: \"" + debug_id + L"\" "
-        L"} }";
+        L"}, "
+        L"use_async_processing: true }";
     wstring response;
     int response_code;