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

chrome/common/extensions/permissions/set_disjunction_permission.h

 // Copyright (c) 2012 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 CHROME_COMMON_EXTENSIONS_PERMISSIONS_SET_DISJUNCTION_PERMISSION_H_
 #define CHROME_COMMON_EXTENSIONS_PERMISSIONS_SET_DISJUNCTION_PERMISSION_H_
 
 #include <algorithm>
 #include <set>
 #include <string>
@@ skipping 92 matching lines @@
         static_cast<const SetDisjunctionPermission*>(rhs);
     scoped_ptr<SetDisjunctionPermission> result(new DerivedType(info()));
     std::set_intersection(
         data_set_.begin(), data_set_.end(),
         perm->data_set_.begin(), perm->data_set_.end(),
         std::inserter<std::set<PermissionDataType> >(
             result->data_set_, result->data_set_.begin()));
     return result->data_set_.empty() ? NULL : result.release();
   }
 
-  virtual bool FromValue(const base::Value* value) OVERRIDE {
+  virtual bool FromValue(const base::Value* value,
+                         std::string* error) OVERRIDE {
     data_set_.clear();
     const base::ListValue* list = NULL;
 
-    if (!value)
+    if (!value || !value->GetAsList(&list) || list->GetSize() == 0) {
+      if (error)
+        *error = "NULL or empty permission list";
       return false;
-
-    if (!value->GetAsList(&list) || list->GetSize() == 0)
-      return false;
+    }
 
     for (size_t i = 0; i < list->GetSize(); ++i) {
-      const base::Value* item_value;
-      if (!list->Get(i, &item_value))
-        return false;
+      const base::Value* item_value = NULL;
+      bool got_item = list->Get(i, &item_value);
+      DCHECK(got_item);
+      DCHECK(item_value);
 
       PermissionDataType data;
-      if (!data.FromValue(item_value))
+      if (!data.FromValue(item_value)) {
+        if (error)
+          *error = "Cannot parse an item from the permission list";
         return false;
+      }
 
       data_set_.insert(data);
     }
     return true;
   }
 
   virtual scoped_ptr<base::Value> ToValue() const OVERRIDE {
     base::ListValue* list = new base::ListValue();
     typename std::set<PermissionDataType>::const_iterator i;
     for (i = data_set_.begin(); i != data_set_.end(); ++i) {
@@ skipping 15 matching lines @@
     IPC::LogParam(data_set_, log);
   }
 
  protected:
   std::set<PermissionDataType> data_set_;
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_COMMON_EXTENSIONS_PERMISSIONS_SET_DISJUNCTION_PERMISSION_H_