Rewrite std::string("") to std::string(), Linux edition.

net/spdy/spdy_write_queue_unittest.cc

Index: net/spdy/spdy_write_queue_unittest.cc
diff --git a/net/spdy/spdy_write_queue_unittest.cc b/net/spdy/spdy_write_queue_unittest.cc
index c295db8a1a5749d59eb601d271693856e8081188..26029e466bc9341ec800c80e751aac8326ce1443 100644
--- a/net/spdy/spdy_write_queue_unittest.cc
+++ b/net/spdy/spdy_write_queue_unittest.cc
@@ -60,7 +60,8 @@ int ProducerToInt(scoped_ptr<SpdyFrameProducer> producer) {
 // -- be careful to not call any functions that expect the session to
 // be there.
 SpdyStream* MakeTestStream(RequestPriority priority) {
-  return new SpdyStream(NULL, "", priority, 0, 0, false, BoundNetLog());
+  return new SpdyStream(
+      NULL, std::string(), priority, 0, 0, false, BoundNetLog());
 }
 
 // Add some frame producers of different priority. The producers