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

dbus/end_to_end_async_unittest.cc

Index: dbus/end_to_end_async_unittest.cc
diff --git a/dbus/end_to_end_async_unittest.cc b/dbus/end_to_end_async_unittest.cc
index 0a3446ecceb734cd02a311f093b6c9303dc2ad86..6943494546fd27f309be5ad5d6f6cc013b93f464 100644
--- a/dbus/end_to_end_async_unittest.cc
+++ b/dbus/end_to_end_async_unittest.cc
@@ -185,7 +185,7 @@ class EndToEndAsyncTest : public testing::Test {
       ASSERT_TRUE(reader.PopString(&response_string));
       response_strings_.push_back(response_string);
     } else {
-      response_strings_.push_back("");
+      response_strings_.push_back(std::string());
     }
     message_loop_.Quit();
   };
@@ -205,7 +205,7 @@ class EndToEndAsyncTest : public testing::Test {
       ASSERT_NE("", error->GetErrorName());
       error_names_.push_back(error->GetErrorName());
     } else {
-      error_names_.push_back("");
+      error_names_.push_back(std::string());
     }
     message_loop_.Quit();
   }