Clean up and fix Utils::ToUTF8String() and Utils::ToUTF16String()

src/DefaultFileSystem.cpp

Index: src/DefaultFileSystem.cpp
===================================================================
--- a/src/DefaultFileSystem.cpp
+++ b/src/DefaultFileSystem.cpp
@@ -46,17 +46,17 @@ namespace
     {
     }
   };
 
 #ifdef WIN32
   // Paths need to be converted from UTF-8 to UTF-16 on Windows.
   std::wstring NormalizePath(const std::string& path)
   {
-    return Utils::ToUTF16String(path, path.length());
+    return Utils::ToUTF16String(path);
   }
 
   #define rename _wrename
   #define remove _wremove
 #else
   // POSIX systems: assume that file system encoding is UTF-8 and just use the
   // file paths as they are.
   #define NormalizePath(path) (path)
@@ -155,17 +155,17 @@ std::string DefaultFileSystem::Resolve(c
 {
   if (basePath == "")
   {
     return path;
   }
   else
   {
 #ifdef _WIN32
-  if (PathIsRelative(Utils::ToUTF16String(path, path.length()).c_str()))
+  if (PathIsRelative(NormalizePath(path).c_str()))
 #else
   if (path.length() && *path.begin() != PATH_SEPARATOR)
 #endif
     {
       return basePath + PATH_SEPARATOR + path;
     }
     else
     {