Add a do_not_sync pref to ExtensionPrefs.

extensions/browser/install_flag.h

 // Copyright 2014 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_BROWSER_EXTENSIONS_INSTALL_FLAG_H_
-#define CHROME_BROWSER_EXTENSIONS_INSTALL_FLAG_H_
+#ifndef EXTENSIONS_BROWSER_INSTALL_FLAG_H_
+#define EXTENSIONS_BROWSER_INSTALL_FLAG_H_
 
 namespace extensions {
 
 // Flags used when installing an extension, through ExtensionService and
 // ExtensionPrefs and beyond.
 enum InstallFlag {
   kInstallFlagNone = 0,
 
   // The requirements of the extension weren't met (for example graphics
   // capabilities).
   kInstallFlagHasRequirementErrors = 1 << 0,
 
   // Extension is blacklisted for being malware.
   kInstallFlagIsBlacklistedForMalware = 1 << 1,
 
   // This is an ephemeral app.
   kInstallFlagIsEphemeral = 1 << 2,
 
   // Install the extension immediately, don't wait until idle.
   kInstallFlagInstallImmediately = 1 << 3,
+
+  // Do not sync the installed extension.
+  kInstallFlagDoNotSync = 1 << 4,
 };
 
 }  // namespace extensions
 
-#endif  // CHROME_BROWSER_EXTENSIONS_INSTALL_FLAG_H_
+#endif  // EXTENSIONS_BROWSER_INSTALL_FLAG_H_