Makes GetComponentExtensionResourceManager() thread-safe.

extensions/browser/component_extension_resource_manager.h

 // Copyright 2014 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_BROWSER_COMPONENT_EXTENSION_RESOURCE_MANAGER_H_
 #define EXTENSIONS_BROWSER_COMPONENT_EXTENSION_RESOURCE_MANAGER_H_
 
 namespace base {
 class FilePath;
 }
 
 namespace extensions {
 
 // This class manages which extension resources actually come from
 // the resource bundle.
 class ComponentExtensionResourceManager {
  public:
   virtual ~ComponentExtensionResourceManager() {}
 
   // Checks whether image is a component extension resource. Returns false
   // if a given |resource| does not have a corresponding image in bundled
   // resources. Otherwise fills |resource_id|. This doesn't check if the
   // extension the resource is in is actually a component extension.
   virtual bool IsComponentExtensionResource(
-    const base::FilePath& extension_path,
-    const base::FilePath& resource_path,
-    int* resource_id) = 0;
+      const base::FilePath& extension_path,
+      const base::FilePath& resource_path,
+      int* resource_id) const = 0;
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_COMPONENT_EXTENSION_RESOURCE_MANAGER_H_