[Extensions] Fix a data race in ChromeExtensionMessageFilter.

extensions/common/file_util.h

 // Copyright 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 EXTENSIONS_COMMON_FILE_UTIL_H_
 #define EXTENSIONS_COMMON_FILE_UTIL_H_
 
 #include <map>
 #include <string>
 #include <vector>
 
 #include "base/files/file_path.h"
 #include "base/memory/ref_counted.h"
 #include "extensions/common/manifest.h"
 #include "extensions/common/message_bundle.h"
 
 class ExtensionIconSet;
 class GURL;
 
 namespace base {
 class FilePath;
 }
 
 namespace extensions {
 class Extension;
-class ExtensionSet;
 struct InstallWarning;
 
 // Utilities for manipulating the on-disk storage of extensions.
 namespace file_util {
 
 extern const base::FilePath::CharType kTempDirectoryName[];
 
 // Sets the flag to enable safe installation (i.e. flush all installed files).
 void SetUseSafeInstallation(bool use_safe_installation);
 
@@ skipping 91 matching lines @@
                                  const std::string& default_locale,
                                  std::string* error);
 
 // Loads the extension message bundle substitution map. Contains at least
 // the extension_id item.
 MessageBundle::SubstitutionMap* LoadMessageBundleSubstitutionMap(
     const base::FilePath& extension_path,
     const std::string& extension_id,
     const std::string& default_locale);
 
-// Loads the extension message bundle substitution map, including messages from
-// Shared Modules that the given extension imports. Contains at least the
-// extension_id item.
-MessageBundle::SubstitutionMap* LoadMessageBundleSubstitutionMapWithImports(
+// Loads the extension message bundle substitution map for a non-localized
+// extension. Contains only the extension_id item.
+// This doesn't require hitting disk, so it's safe to call on any thread.
+MessageBundle::SubstitutionMap* LoadNonLocalizedMessageBundleSubstitutionMap(
+    const std::string& extension_id);
+
+// Loads the extension message bundle substitution map from the specified paths.
+// Contains at least the extension_id item.
+MessageBundle::SubstitutionMap* LoadMessageBundleSubstitutionMapFromPaths(
+    const std::vector<base::FilePath>& paths,
     const std::string& extension_id,
-    const ExtensionSet& extension_set);
+    const std::string& default_locale);
 
 // Helper functions for getting paths for files used in content verification.
 base::FilePath GetVerifiedContentsPath(const base::FilePath& extension_path);
 base::FilePath GetComputedHashesPath(const base::FilePath& extension_path);
 
 }  // namespace file_util
 }  // namespace extensions
 
 #endif  // EXTENSIONS_COMMON_FILE_UTIL_H_