Remove SpdyString wrapper for std::string.

This used to be needed before std::string was used internally.
QuicString has already been removed at 238124961.

gfe-relnote: n/a, no functional change.
PiperOrigin-RevId: 263689054
Change-Id: Ib6f8d4c060f5f557caf88c75389cd2df727ac017
diff --git a/spdy/core/spdy_prefixed_buffer_reader_test.cc b/spdy/core/spdy_prefixed_buffer_reader_test.cc
index f570dfc..a0f9257 100644
--- a/spdy/core/spdy_prefixed_buffer_reader_test.cc
+++ b/spdy/core/spdy_prefixed_buffer_reader_test.cc
@@ -4,7 +4,8 @@
 
 #include "net/third_party/quiche/src/spdy/core/spdy_prefixed_buffer_reader.h"
 
-#include "net/third_party/quiche/src/spdy/platform/api/spdy_string.h"
+#include <string>
+
 #include "net/third_party/quiche/src/spdy/platform/api/spdy_string_piece.h"
 #include "net/third_party/quiche/src/spdy/platform/api/spdy_test.h"
 
@@ -16,14 +17,14 @@
 
 class SpdyPrefixedBufferReaderTest : public ::testing::Test {
  protected:
-  SpdyPrefixedBufferReader Build(const SpdyString& prefix,
-                                 const SpdyString& suffix) {
+  SpdyPrefixedBufferReader Build(const std::string& prefix,
+                                 const std::string& suffix) {
     prefix_ = prefix;
     suffix_ = suffix;
     return SpdyPrefixedBufferReader(prefix_.data(), prefix_.length(),
                                     suffix_.data(), suffix_.length());
   }
-  SpdyString prefix_, suffix_;
+  std::string prefix_, suffix_;
 };
 
 TEST_F(SpdyPrefixedBufferReaderTest, ReadRawFromPrefix) {