GN: Store parse error messages (so they aren't dropped due to races)

tools/gn/input_file_manager.h

 // 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.
 
 #ifndef TOOLS_GN_INPUT_FILE_MANAGER_H_
 #define TOOLS_GN_INPUT_FILE_MANAGER_H_
 
 #include <set>
 #include <utility>
 #include <vector>
@@ skipping 99 matching lines @@
 
     // Event to signal when the load is complete (or fails). This is lazily
     // created only when a thread is synchronously waiting for this load (which
     // only happens for imports).
     scoped_ptr<base::WaitableEvent> completion_event;
 
     std::vector<Token> tokens;
 
     // Null before the file is loaded or if loading failed.
     scoped_ptr<ParseNode> parsed_root;
+    scoped_ptr<Err> parse_error;

[brettw, 2014/10/14 17:13:09]

You should be able to make this a raw "Err" object. Since an err has a "no
error" state on it (the default constructor).

[cjhopman, 2014/10/16 18:26:02]

Done.

   };
 
   virtual ~InputFileManager();
 
   void BackgroundLoadFile(const LocationRange& origin,
                           const BuildSettings* build_settings,
                           const SourceFile& name,
                           InputFile* file);
 
   // Loads the given file. On error, sets the Err and return false.
@@ skipping 16 matching lines @@
   //
   // See AddDynamicInput().
   //
   // Owning pointers.
   std::vector<InputFileData*> dynamic_inputs_;
 
   DISALLOW_COPY_AND_ASSIGN(InputFileManager);
 };
 
 #endif  // TOOLS_GN_INPUT_FILE_MANAGER_H_