GN: Make file/dir resolving return errors.

tools/gn/functions.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "tools/gn/functions.h"
 
 #include <iostream>
 
 #include "base/environment.h"
 #include "base/strings/string_util.h"
@@ skipping 473 matching lines @@
 
 Value RunImport(Scope* scope,
                 const FunctionCallNode* function,
                 const std::vector<Value>& args,
                 Err* err) {
   if (!EnsureSingleStringArg(function, args, err))
     return Value();
 
   const SourceDir& input_dir = scope->GetSourceDir();
   SourceFile import_file =
-      input_dir.ResolveRelativeFile(args[0].string_value(),
+      input_dir.ResolveRelativeFile(args[0], err,
           scope->settings()->build_settings()->root_path_utf8());
-  scope->settings()->import_manager().DoImport(import_file, function,
-                                               scope, err);
+  if (!err->has_error()) {
+    scope->settings()->import_manager().DoImport(import_file, function,
+                                                 scope, err);
+  }
   return Value();
 }
 
 // set_sources_assignment_filter -----------------------------------------------
 
 const char kSetSourcesAssignmentFilter[] = "set_sources_assignment_filter";
 const char kSetSourcesAssignmentFilter_HelpShort[] =
     "set_sources_assignment_filter: Set a pattern to filter source files.";
 const char kSetSourcesAssignmentFilter_Help[] =
     "set_sources_assignment_filter: Set a pattern to filter source files.\n"
@@ skipping 307 matching lines @@
   }
 
   // Otherwise it's a no-block function.
   if (!VerifyNoBlockForFunctionCall(function, block, err))
     return Value();
   return found_function->second.no_block_runner(scope, function,
                                                 args.list_value(), err);
 }
 
 }  // namespace functions