Move ReadFileToString to the base namespace.

courgette/courgette_tool.cc

Index: courgette/courgette_tool.cc
diff --git a/courgette/courgette_tool.cc b/courgette/courgette_tool.cc
index 1d8b77d813daab32f52fb77d4f335e98bcd48117..3b231f8957f42b6ebd88dc3a6bfb83dc9e56631f 100644
--- a/courgette/courgette_tool.cc
+++ b/courgette/courgette_tool.cc
@@ -53,7 +53,7 @@ std::string ReadOrFail(const base::FilePath& file_name, const char* kind) {
     Problem("Can't read %s file.", kind);
   std::string buffer;
   buffer.reserve(static_cast<size_t>(file_size));
-  if (!file_util::ReadFileToString(file_name, &buffer))
+  if (!base::ReadFileToString(file_name, &buffer))
     Problem("Can't read %s file.", kind);
   return buffer;
 }