GN: Make file/dir resolving return errors.

tools/gn/function_get_path_info.cc

Index: tools/gn/function_get_path_info.cc
diff --git a/tools/gn/function_get_path_info.cc b/tools/gn/function_get_path_info.cc
index a3f2c109301c120ddf01f4a7c4f7da45b2660db2..e79afcafb2fec561aa72426fd78a26c84045e9fa 100644
--- a/tools/gn/function_get_path_info.cc
+++ b/tools/gn/function_get_path_info.cc
@@ -28,15 +28,19 @@ enum What {
 // |current_dir|), regardless of whether the input is a directory or a file.
 SourceDir DirForInput(const Settings* settings,
                       const SourceDir& current_dir,
-                      const std::string& input_string) {
+                      const Value& input,
+                      Err* err) {
+  // Input should already have been validated as a string.
+  const std::string& input_string = input.string_value();
+
   if (!input_string.empty() && input_string[input_string.size() - 1] == '/') {
     // Input is a directory.
-    return current_dir.ResolveRelativeDir(input_string,
+    return current_dir.ResolveRelativeDir(input, err,
         settings->build_settings()->root_path_utf8());
   }
 
   // Input is a directory.
-  return current_dir.ResolveRelativeFile(input_string,
+  return current_dir.ResolveRelativeFile(input, err,
       settings->build_settings()->root_path_utf8()).GetDir();
 }
 
@@ -85,21 +89,21 @@ std::string GetOnePathInfo(const Settings* settings,
       return DirectoryWithNoLastSlash(
           GetGenDirForSourceDir(settings,
                                 DirForInput(settings, current_dir,
-                                            input_string)));
+                                            input, err)));
     }
     case WHAT_OUT_DIR: {
       return DirectoryWithNoLastSlash(
           GetOutputDirForSourceDir(settings,
                                    DirForInput(settings, current_dir,
-                                               input_string)));
+                                               input, err)));
     }
     case WHAT_ABSPATH: {
       if (!input_string.empty() &&
           input_string[input_string.size() - 1] == '/') {
-        return current_dir.ResolveRelativeDir(input_string,
+        return current_dir.ResolveRelativeDir(input, err,
             settings->build_settings()->root_path_utf8()).value();
       } else {
-        return current_dir.ResolveRelativeFile(input_string,
+        return current_dir.ResolveRelativeFile(input, err,
             settings->build_settings()->root_path_utf8()).value();
       }
     }