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

chrome/browser/net/http_pipelining_compatibility_client_unittest.cc

Index: chrome/browser/net/http_pipelining_compatibility_client_unittest.cc
diff --git a/chrome/browser/net/http_pipelining_compatibility_client_unittest.cc b/chrome/browser/net/http_pipelining_compatibility_client_unittest.cc
index 7f3379041512dfe06cdf0f7a3e8c9bdff703bbf8..f582d1b6133972a33e97bc4ca71630fe091039d2 100644
--- a/chrome/browser/net/http_pipelining_compatibility_client_unittest.cc
+++ b/chrome/browser/net/http_pipelining_compatibility_client_unittest.cc
@@ -118,8 +118,10 @@ class HttpPipeliningCompatibilityClientTest : public testing::Test {
       HttpPipeliningCompatibilityClient::Options options) {
     HttpPipeliningCompatibilityClient client(NULL);
     net::TestCompletionCallback callback;
-    client.Start(test_server_.GetURL("").spec(),
-                 requests, options, callback.callback(),
+    client.Start(test_server_.GetURL(std::string()).spec(),
+                 requests,
+                 options,
+                 callback.callback(),
                  context_->GetURLRequestContext());
     callback.WaitForResult();
   }