diff --git a/http2/decoder/decode_http2_structures_test.cc b/http2/decoder/decode_http2_structures_test.cc
index 91b3ef7..48b79bd 100644
--- a/http2/decoder/decode_http2_structures_test.cc
+++ b/http2/decoder/decode_http2_structures_test.cc
@@ -9,13 +9,14 @@
 
 #include <stddef.h>
 
+#include <string>
+
 #include "testing/gtest/include/gtest/gtest.h"
 #include "net/third_party/quiche/src/http2/decoder/decode_buffer.h"
 #include "net/third_party/quiche/src/http2/decoder/decode_status.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/platform/api/http2_string_piece.h"
 #include "net/third_party/quiche/src/http2/test_tools/http2_random.h"
 #include "net/third_party/quiche/src/http2/tools/http2_frame_builder.h"
@@ -32,7 +33,7 @@
 }
 
 template <class S>
-Http2String SerializeStructure(const S& s) {
+std::string SerializeStructure(const S& s) {
   Http2FrameBuilder fb;
   fb.Append(s);
   EXPECT_EQ(S::EncodedSize(), fb.size());
@@ -70,7 +71,7 @@
   // Encode the structure |in_s| into bytes, then decode the bytes
   // and validate that the decoder produced the same field values.
   void EncodeThenDecode(const S& in_s) {
-    Http2String bytes = SerializeStructure(in_s);
+    std::string bytes = SerializeStructure(in_s);
     EXPECT_EQ(S::EncodedSize(), bytes.size());
     DecodeLeadingStructure(&in_s, bytes);
   }
diff --git a/http2/decoder/http2_frame_decoder_test.cc b/http2/decoder/http2_frame_decoder_test.cc
index 50e75ed..7ed67f3 100644
--- a/http2/decoder/http2_frame_decoder_test.cc
+++ b/http2/decoder/http2_frame_decoder_test.cc
@@ -6,13 +6,13 @@
 
 // Tests of Http2FrameDecoder.
 
+#include <string>
 #include <vector>
 
 #include "testing/gtest/include/gtest/gtest.h"
 #include "net/third_party/quiche/src/http2/http2_constants.h"
 #include "net/third_party/quiche/src/http2/platform/api/http2_logging.h"
 #include "net/third_party/quiche/src/http2/platform/api/http2_reconstruct_object.h"
-#include "net/third_party/quiche/src/http2/platform/api/http2_string.h"
 #include "net/third_party/quiche/src/http2/platform/api/http2_string_piece.h"
 #include "net/third_party/quiche/src/http2/platform/api/http2_test_helpers.h"
 #include "net/third_party/quiche/src/http2/test_tools/frame_parts.h"
@@ -84,7 +84,7 @@
     // The decoder will discard the remaining bytes, but not go beyond that,
     // which these conditions verify.
     size_t extra = 10;
-    Http2String junk(remaining + extra, '0');
+    std::string junk(remaining + extra, '0');
     DecodeBuffer tmp(junk);
     EXPECT_EQ(DecodeStatus::kDecodeDone, decoder_.DecodeFrame(&tmp));
     EXPECT_EQ(remaining, tmp.Offset());
@@ -147,8 +147,8 @@
     VERIFY_GT(slow_decode_count_, 0u);
 
     // Repeat with more input; it should stop without reading that input.
-    Http2String next_frame = Random().RandString(10);
-    Http2String input(payload.data(), payload.size());
+    std::string next_frame = Random().RandString(10);
+    std::string input(payload.data(), payload.size());
     input += next_frame;
 
     ResetDecodeSpeedCounters();
diff --git a/http2/decoder/http2_structure_decoder_test.cc b/http2/decoder/http2_structure_decoder_test.cc
index 7b9afc5..2545109 100644
--- a/http2/decoder/http2_structure_decoder_test.cc
+++ b/http2/decoder/http2_structure_decoder_test.cc
@@ -21,6 +21,7 @@
 #include <stddef.h>
 
 #include <cstdint>
+#include <string>
 
 #include "testing/gtest/include/gtest/gtest.h"
 #include "net/third_party/quiche/src/http2/decoder/decode_buffer.h"
@@ -29,7 +30,6 @@
 #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_reconstruct_object.h"
-#include "net/third_party/quiche/src/http2/platform/api/http2_string.h"
 #include "net/third_party/quiche/src/http2/platform/api/http2_string_piece.h"
 #include "net/third_party/quiche/src/http2/platform/api/http2_test_helpers.h"
 #include "net/third_party/quiche/src/http2/tools/http2_frame_builder.h"
@@ -159,7 +159,7 @@
   // Encode the structure |in_s| into bytes, then decode the bytes
   // and validate that the decoder produced the same field values.
   AssertionResult EncodeThenDecode(const S& in_s) {
-    Http2String bytes = SerializeStructure(in_s);
+    std::string bytes = SerializeStructure(in_s);
     VERIFY_EQ(S::EncodedSize(), bytes.size());
     VERIFY_AND_RETURN_SUCCESS(DecodeLeadingStructure(&in_s, bytes));
   }
diff --git a/http2/decoder/payload_decoders/altsvc_payload_decoder_test.cc b/http2/decoder/payload_decoders/altsvc_payload_decoder_test.cc
index 6a4bee5..354fdae 100644
--- a/http2/decoder/payload_decoders/altsvc_payload_decoder_test.cc
+++ b/http2/decoder/payload_decoders/altsvc_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"
@@ -103,8 +104,8 @@
                                             ::testing::Values(0, 1, 3, 65537)));
 
 TEST_P(AltSvcPayloadLengthTests, ValidOriginAndValueLength) {
-  Http2String origin = Random().RandString(origin_length_);
-  Http2String value = Random().RandString(value_length_);
+  std::string origin = Random().RandString(origin_length_);
+  std::string value = Random().RandString(value_length_);
   Http2FrameBuilder fb;
   fb.Append(Http2AltSvcFields{origin_length_});
   fb.Append(origin);
diff --git a/http2/decoder/payload_decoders/continuation_payload_decoder_test.cc b/http2/decoder/payload_decoders/continuation_payload_decoder_test.cc
index 35479a1..125e16f 100644
--- a/http2/decoder/payload_decoders/continuation_payload_decoder_test.cc
+++ b/http2/decoder/payload_decoders/continuation_payload_decoder_test.cc
@@ -6,6 +6,7 @@
 
 #include <stddef.h>
 
+#include <string>
 #include <type_traits>
 
 #include "testing/gtest/include/gtest/gtest.h"
@@ -14,7 +15,6 @@
 #include "net/third_party/quiche/src/http2/http2_constants.h"
 #include "net/third_party/quiche/src/http2/http2_structures.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/tools/random_decoder_test.h"
@@ -73,7 +73,7 @@
                          ::testing::Values(0, 1, 2, 3, 4, 5, 6));
 
 TEST_P(ContinuationPayloadDecoderTest, ValidLength) {
-  Http2String hpack_payload = Random().RandString(length_);
+  std::string hpack_payload = Random().RandString(length_);
   Http2FrameHeader frame_header(length_, Http2FrameType::CONTINUATION,
                                 RandFlags(), RandStreamId());
   set_frame_header(frame_header);
diff --git a/http2/decoder/payload_decoders/data_payload_decoder_test.cc b/http2/decoder/payload_decoders/data_payload_decoder_test.cc
index 1cae714..f1dc017 100644
--- a/http2/decoder/payload_decoders/data_payload_decoder_test.cc
+++ b/http2/decoder/payload_decoders/data_payload_decoder_test.cc
@@ -6,6 +6,8 @@
 
 #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"
@@ -13,7 +15,6 @@
 #include "net/third_party/quiche/src/http2/http2_structures.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/platform/api/http2_test_helpers.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"
@@ -84,7 +85,7 @@
     Reset();
     uint8_t flags = RandFlags();
 
-    Http2String data_payload = Random().RandString(data_size);
+    std::string data_payload = Random().RandString(data_size);
     frame_builder_.Append(data_payload);
     MaybeAppendTrailingPadding();
 
diff --git a/http2/decoder/payload_decoders/goaway_payload_decoder_test.cc b/http2/decoder/payload_decoders/goaway_payload_decoder_test.cc
index 5ea533a..b2d96fb 100644
--- a/http2/decoder/payload_decoders/goaway_payload_decoder_test.cc
+++ b/http2/decoder/payload_decoders/goaway_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"
@@ -92,7 +93,7 @@
 TEST_P(GoAwayOpaqueDataLengthTests, ValidLength) {
   Http2GoAwayFields goaway;
   Randomize(&goaway, RandomPtr());
-  Http2String opaque_data = Random().RandString(length_);
+  std::string opaque_data = Random().RandString(length_);
   Http2FrameBuilder fb;
   fb.Append(goaway);
   fb.Append(opaque_data);
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();
diff --git a/http2/decoder/payload_decoders/payload_decoder_base_test_util.h b/http2/decoder/payload_decoders/payload_decoder_base_test_util.h
index 66dd88a..5de0d1b 100644
--- a/http2/decoder/payload_decoders/payload_decoder_base_test_util.h
+++ b/http2/decoder/payload_decoders/payload_decoder_base_test_util.h
@@ -9,6 +9,8 @@
 
 #include <stddef.h>
 
+#include <string>
+
 #include "testing/gtest/include/gtest/gtest.h"
 #include "net/third_party/quiche/src/http2/decoder/decode_buffer.h"
 #include "net/third_party/quiche/src/http2/decoder/decode_status.h"
@@ -19,7 +21,6 @@
 #include "net/third_party/quiche/src/http2/http2_structures.h"
 #include "net/third_party/quiche/src/http2/platform/api/http2_logging.h"
 #include "net/third_party/quiche/src/http2/platform/api/http2_reconstruct_object.h"
-#include "net/third_party/quiche/src/http2/platform/api/http2_string.h"
 #include "net/third_party/quiche/src/http2/platform/api/http2_string_piece.h"
 #include "net/third_party/quiche/src/http2/test_tools/frame_parts.h"
 #include "net/third_party/quiche/src/http2/tools/http2_frame_builder.h"
@@ -429,7 +430,7 @@
     }
 
     HTTP2_VLOG(1) << "payload_length=" << payload_length;
-    Http2String payload = fb.buffer().substr(0, payload_length);
+    std::string payload = fb.buffer().substr(0, payload_length);
 
     // The missing length is the amount we cut off the end, unless
     // payload_length is zero, in which case the decoder knows only that 1
diff --git a/http2/decoder/payload_decoders/push_promise_payload_decoder_test.cc b/http2/decoder/payload_decoders/push_promise_payload_decoder_test.cc
index 64dd935..0561aa4 100644
--- a/http2/decoder/payload_decoders/push_promise_payload_decoder_test.cc
+++ b/http2/decoder/payload_decoders/push_promise_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"
@@ -98,7 +99,7 @@
     HTTP2_LOG(INFO) << "###########   hpack_size = " << hpack_size
                     << "  ###########";
     Reset();
-    Http2String hpack_payload = Random().RandString(hpack_size);
+    std::string hpack_payload = Random().RandString(hpack_size);
     Http2PushPromiseFields push_promise{RandStreamId()};
     frame_builder_.Append(push_promise);
     frame_builder_.Append(hpack_payload);
diff --git a/http2/decoder/payload_decoders/unknown_payload_decoder_test.cc b/http2/decoder/payload_decoders/unknown_payload_decoder_test.cc
index 018bd82..1075932 100644
--- a/http2/decoder/payload_decoders/unknown_payload_decoder_test.cc
+++ b/http2/decoder/payload_decoders/unknown_payload_decoder_test.cc
@@ -6,6 +6,7 @@
 
 #include <stddef.h>
 
+#include <string>
 #include <type_traits>
 
 #include "testing/gtest/include/gtest/gtest.h"
@@ -14,7 +15,6 @@
 #include "net/third_party/quiche/src/http2/http2_constants.h"
 #include "net/third_party/quiche/src/http2/http2_structures.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"
@@ -83,7 +83,7 @@
                          ::testing::Values(0, 1, 2, 3, 255, 256));
 
 TEST_P(UnknownPayloadDecoderTest, ValidLength) {
-  Http2String unknown_payload = Random().RandString(length_);
+  std::string unknown_payload = Random().RandString(length_);
   Http2FrameHeader frame_header(length_, g_unknown_frame_type, Random().Rand8(),
                                 RandStreamId());
   set_frame_header(frame_header);