Prevent extension sideloading from Windows registry

extensions/common/extension.h

 // Copyright (c) 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_EXTENSION_H_
 #define EXTENSIONS_COMMON_EXTENSION_H_
 
 #include <algorithm>
 #include <iosfwd>
 #include <map>
@@ skipping 148 matching lines @@
 
     // |WAS_INSTALLED_BY_OEM| installed by an OEM (e.g on Chrome OS) and should
     // be placed in a special OEM folder in the App Launcher. Note: OEM apps are
     // also installed by Default (i.e. WAS_INSTALLED_BY_DEFAULT is also true).
     WAS_INSTALLED_BY_OEM = 1 << 10,
 
     // |WAS_INSTALLED_BY_CUSTODIAN| means this extension was installed by the
     // custodian of a supervised user.
     WAS_INSTALLED_BY_CUSTODIAN = 1 << 11,
 
+    // |MAY_BE_UNTRUSTED| indicates that this extension came from a potentially
+    // unsafe source (e.g., sideloaded from a local CRX file via the Windows
+    // registry). Such extensions may be subjected to additional constraints
+    // before they are fully installed and enabled.
+    MAY_BE_UNTRUSTED = 1 << 12,
+
     // When adding new flags, make sure to update kInitFromValueFlagBits.
   };
 
   // This is the highest bit index of the flags defined above.
   static const int kInitFromValueFlagBits;
 
   static scoped_refptr<Extension> Create(const base::FilePath& path,
                                          Manifest::Location location,
                                          const base::DictionaryValue& value,
                                          int flags,
@@ skipping 382 matching lines @@
 
   UpdatedExtensionPermissionsInfo(
       const Extension* extension,
       const PermissionSet* permissions,
       Reason reason);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_COMMON_EXTENSION_H_