Enable/disable extensions upon changes in blacklist.

extensions/common/extension.h

Index: extensions/common/extension.h
diff --git a/extensions/common/extension.h b/extensions/common/extension.h
index fb2cf4c429cea6e5a7793ede64a8b1ddd478d666..ead3dd0fb2d69aefceb930abf41d53811722b1b7 100644
--- a/extensions/common/extension.h
+++ b/extensions/common/extension.h
@@ -90,9 +90,9 @@ class Extension : public base::RefCountedThreadSafe<Extension> {
     DISABLE_UNKNOWN_FROM_SYNC = 1 << 5,
     DISABLE_PERMISSIONS_CONSENT = 1 << 6,  // Unused - abandoned experiment.
     DISABLE_KNOWN_DISABLED = 1 << 7,
-
-    // Disabled because we could not verify the install.
-    DISABLE_NOT_VERIFIED = 1 << 8,
+    DISABLE_NOT_VERIFIED = 1 << 8,  // Disabled because we could not verify
+                                    // the install.
+    DISABLE_GREYLIST = 1 << 9
   };
 
   enum InstallType {