Add a do_not_sync pref to ExtensionPrefs.

extensions/browser/install_flag.h

Index: extensions/browser/install_flag.h
diff --git a/extensions/browser/install_flag.h b/extensions/browser/install_flag.h
index b8eac9906988b6dca599fce1526d3b0844327532..f157a6e356573d6726114b65081f5f456224e249 100644
--- a/extensions/browser/install_flag.h
+++ b/extensions/browser/install_flag.h
@@ -2,8 +2,8 @@
 // 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 {
 
@@ -24,8 +24,11 @@ enum InstallFlag {
 
   // 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_