[Extensions] Log instances of invalid extensions being added

extensions/common/manifest.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_MANIFEST_H_
 #define EXTENSIONS_COMMON_MANIFEST_H_
 
 #include <map>
 #include <memory>
 #include <set>
@@ skipping 92 matching lines @@
     return location == EXTERNAL_POLICY ||
            location == EXTERNAL_POLICY_DOWNLOAD;
   }
 
   // Whether the |location| is an extension intended to be an internal part of
   // Chrome.
   static inline bool IsComponentLocation(Location location) {
     return location == COMPONENT || location == EXTERNAL_COMPONENT;
   }
 
+  static inline bool IsValidLocation(Location location) {
+    return location > INVALID_LOCATION && location < NUM_LOCATIONS;
+  }
+
   // Unpacked extensions start off with file access since they are a developer
   // feature.
   static inline bool ShouldAlwaysAllowFileAccess(Location location) {
     return IsUnpackedLocation(location);
   }
 
   Manifest(Location location, std::unique_ptr<base::DictionaryValue> value);
   virtual ~Manifest();
 
   const std::string& extension_id() const { return extension_id_; }
@@ skipping 71 matching lines @@
   std::unique_ptr<base::DictionaryValue> value_;
 
   Type type_;
 
   DISALLOW_COPY_AND_ASSIGN(Manifest);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_COMMON_MANIFEST_H_