Add UMA logging of extension creation flags.

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 99 matching lines @@
     NEW_INSTALL
   };
 
   // A base class for parsed manifest data that APIs want to store on
   // the extension. Related to base::SupportsUserData, but with an immutable
   // thread-safe interface to match Extension.
   struct ManifestData {
     virtual ~ManifestData() {}
   };
 
+  // Do not change the order of entries or remove entries in this list
+  // as this is used in UMA_HISTOGRAM_ENUMERATIONs about extensions.
   enum InitFromValueFlags {
     NO_FLAGS = 0,
 
     // Usually, the id of an extension is generated by the "key" property of
     // its manifest, but if |REQUIRE_KEY| is not set, a temporary ID will be
     // generated based on the path.
     REQUIRE_KEY = 1 << 0,
 
     // Requires the extension to have an up-to-date manifest version.
     // Typically, we'll support multiple manifest versions during a version
@@ skipping 32 matching lines @@
     REQUIRE_PERMISSIONS_CONSENT = 1 << 8,
 
     // |IS_EPHEMERAL| identifies ephemeral apps (experimental), which are not
     // permanently installed.
     IS_EPHEMERAL = 1 << 9,
 
     // |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,
+
+    // 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,
                                          std::string* error);
 
   // In a few special circumstances, we want to create an Extension and give it
   // an explicit id. Most consumers should just use the other Create() method.
   static scoped_refptr<Extension> Create(const base::FilePath& path,
                                          Manifest::Location location,
@@ skipping 363 matching lines @@
 
   UpdatedExtensionPermissionsInfo(
       const Extension* extension,
       const PermissionSet* permissions,
       Reason reason);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_COMMON_EXTENSION_H_