Use chrome_constants rather than hardcoded Preferences string in startup_test.cc.

chrome/test/perf/startup_test.cc

Index: chrome/test/perf/startup_test.cc
diff --git a/chrome/test/perf/startup_test.cc b/chrome/test/perf/startup_test.cc
index e15048ebd5b962471c71ccb159bb5ef474405666..34a83dd1c20ea4156c5c19298d891d95c363ab35 100644
--- a/chrome/test/perf/startup_test.cc
+++ b/chrome/test/perf/startup_test.cc
@@ -110,11 +110,11 @@ class StartupTest : public UIPerfTest {
       return;
 
     const base::FilePath pref_template_path(user_data_dir().
-        AppendASCII("Default").
+        AppendASCII(chrome::kInitialProfile).
         AppendASCII("PreferencesTemplate"));
     const base::FilePath pref_path(user_data_dir().
         AppendASCII(TestingProfile::kTestUserProfileDir).
-        AppendASCII("Preferences"));
+        Append(chrome::kPreferencesFilename));
 
     // Read in preferences template.
     std::string pref_string;