Remove Http2String wrapper for std::string.

gfe-relnote: n/a, no functional change.
PiperOrigin-RevId: 263816460
Change-Id: I4f365540414e6a3d78fd00ce6b39a4cdd4c14140
diff --git a/http2/decoder/payload_decoders/headers_payload_decoder_test.cc b/http2/decoder/payload_decoders/headers_payload_decoder_test.cc
index a7a90bf..4e0f2e3 100644
--- a/http2/decoder/payload_decoders/headers_payload_decoder_test.cc
+++ b/http2/decoder/payload_decoders/headers_payload_decoder_test.cc
@@ -6,13 +6,14 @@
 
 #include <stddef.h>
 
+#include <string>
+
 #include "testing/gtest/include/gtest/gtest.h"
 #include "net/third_party/quiche/src/http2/decoder/http2_frame_decoder_listener.h"
 #include "net/third_party/quiche/src/http2/decoder/payload_decoders/payload_decoder_base_test_util.h"
 #include "net/third_party/quiche/src/http2/http2_constants.h"
 #include "net/third_party/quiche/src/http2/http2_structures_test_util.h"
 #include "net/third_party/quiche/src/http2/platform/api/http2_logging.h"
-#include "net/third_party/quiche/src/http2/platform/api/http2_string.h"
 #include "net/third_party/quiche/src/http2/test_tools/frame_parts.h"
 #include "net/third_party/quiche/src/http2/test_tools/frame_parts_collector.h"
 #include "net/third_party/quiche/src/http2/test_tools/http2_random.h"
@@ -116,7 +117,7 @@
         frame_builder_.Append(priority);
       }
 
-      Http2String hpack_payload = Random().RandString(hpack_size);
+      std::string hpack_payload = Random().RandString(hpack_size);
       frame_builder_.Append(hpack_payload);
 
       MaybeAppendTrailingPadding();