Add SpdyString alias for std::string in net/spdy.

net/spdy/spdy_session_test_util.cc

Index: net/spdy/spdy_session_test_util.cc
diff --git a/net/spdy/spdy_session_test_util.cc b/net/spdy/spdy_session_test_util.cc
index 36e4c57f9f126f3ceb22e6a71022c51a3e3752b8..86939c40aa9b76f32bd08eaea894544a24c1ed60 100644
--- a/net/spdy/spdy_session_test_util.cc
+++ b/net/spdy/spdy_session_test_util.cc
@@ -10,11 +10,9 @@
 namespace net {
 
 SpdySessionTestTaskObserver::SpdySessionTestTaskObserver(
-    const std::string& file_name,
-    const std::string& function_name)
-    : executed_count_(0),
-      file_name_(file_name),
-      function_name_(function_name) {
+    const SpdyString& file_name,
+    const SpdyString& function_name)
+    : executed_count_(0), file_name_(file_name), function_name_(function_name) {
   base::MessageLoop::current()->AddTaskObserver(this);
 }