Fixes integer overflow in OgHttp2Session::UpdateInitialWindowSize().

Before:
  http://sponge2/319b4db9-8c08-4432-8702-75a90fb964e5

After:
  http://sponge2/446d71a9-88b7-4696-84a1-3a3701384ca2
PiperOrigin-RevId: 427764038

http2/adapter/oghttp2_session.cc

diff --git a/http2/adapter/oghttp2_session.cc b/http2/adapter/oghttp2_session.cc
index 6cdbff7..8a85c36 100644
--- a/http2/adapter/oghttp2_session.cc
+++ b/http2/adapter/oghttp2_session.cc
@@ -1768,8 +1768,9 @@
     if (new_window_size > spdy::kSpdyMaximumWindowSize) {
       EnqueueFrame(absl::make_unique<spdy::SpdyRstStreamIR>(
           stream_id, spdy::ERROR_CODE_FLOW_CONTROL_ERROR));
+    } else {
+      stream_state.send_window += delta;
     }
-    stream_state.send_window += delta;
     if (current_window_size <= 0 && new_window_size > 0) {
       write_scheduler_.MarkStreamReady(stream_id, false);
     }