Extensions: Make it possible for permission parsing code to return a detailed error message.

extensions/common/permissions/api_permission.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_PERMISSIONS_API_PERMISSION_H_
 #define EXTENSIONS_COMMON_PERMISSIONS_API_PERMISSION_H_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 186 matching lines @@
 
   // Returns true if the given permission is allowed.
   virtual bool Check(const CheckParam* param) const = 0;
 
   // Returns true if |rhs| is a subset of this.
   virtual bool Contains(const APIPermission* rhs) const = 0;
 
   // Returns true if |rhs| is equal to this.
   virtual bool Equal(const APIPermission* rhs) const = 0;
 
-  // Parses the APIPermission from |value|. Returns false if error happens.
-  virtual bool FromValue(const base::Value* value) = 0;
+  // Parses the APIPermission from |value|. Returns false if an error happens
+  // and optionally set |error| if |error| is not NULL.
+  virtual bool FromValue(const base::Value* value, std::string* error) = 0;
 
   // Stores this into a new created |value|.
   virtual scoped_ptr<base::Value> ToValue() const = 0;
 
   // Clones this.
   virtual APIPermission* Clone() const = 0;
 
   // Returns a new API permission which equals this - |rhs|.
   virtual APIPermission* Diff(const APIPermission* rhs) const = 0;
 
@@ skipping 112 matching lines @@
   const char* const name_;
   const int flags_;
   const int l10n_message_id_;
   const PermissionMessage::ID message_id_;
   const APIPermissionConstructor api_permission_constructor_;
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_COMMON_PERMISSIONS_API_PERMISSION_H_