Remove |using base::StringPiece| from net/spdy header files.

net/spdy/spdy_test_utils.h

Index: net/spdy/spdy_test_utils.h
diff --git a/net/spdy/spdy_test_utils.h b/net/spdy/spdy_test_utils.h
index a9ff5f38784775e7bbbf9ef2c33d1742efea8955..fee91f68dd7412d97baf97fac6bbf133643f84a2 100644
--- a/net/spdy/spdy_test_utils.h
+++ b/net/spdy/spdy_test_utils.h
@@ -17,9 +17,9 @@ namespace net {
 class HashValue;
 class TransportSecurityState;
 
-inline bool operator==(StringPiece x,
+inline bool operator==(base::StringPiece x,
                        const SpdyHeaderBlock::StringPieceProxy& y) {
-  return x == y.operator StringPiece();
+  return x == y.operator base::StringPiece();
 }
 
 namespace test {