Move ReadFileToString to the base namespace.

testing/android/native_test_util.cc

Index: testing/android/native_test_util.cc
diff --git a/testing/android/native_test_util.cc b/testing/android/native_test_util.cc
index c0ea7b0fef82d66ce3381401c4aa0d6981975df5..ff2c47ebf7de7dd34e80c0c4dabfa1ca21bd2652 100644
--- a/testing/android/native_test_util.cc
+++ b/testing/android/native_test_util.cc
@@ -31,7 +31,7 @@ void ParseArgsFromCommandLineFile(
     const char* path, std::vector<std::string>* args) {
   base::FilePath command_line(path);
   std::string command_line_string;
-  if (file_util::ReadFileToString(command_line, &command_line_string)) {
+  if (base::ReadFileToString(command_line, &command_line_string)) {
     ParseArgsFromString(command_line_string, args);
   }
 }