Fix install verification for sideloaded extensions without update urls

chrome/browser/extensions/install_verifier.h

Index: chrome/browser/extensions/install_verifier.h
diff --git a/chrome/browser/extensions/install_verifier.h b/chrome/browser/extensions/install_verifier.h
index 7c7c3ee8ae74a02011ea16f248c0822f8b8b3fae..62885ce8d9c567294af02069d19b0cd432323ff3 100644
--- a/chrome/browser/extensions/install_verifier.h
+++ b/chrome/browser/extensions/install_verifier.h
@@ -56,6 +56,10 @@ class InstallVerifier : public ManagementPolicy::Provider {
   // Returns the timestamp of our InstallSignature, if we have one.
   base::Time SignatureTimestamp();
 
+  // Returns true if |id| is either verified or our stored signature explicitly
+  // tells us that it was invalid when we asked the server about it.
+  bool IsKnownId(const std::string& id);
+
   // A callback for indicating success/failure of adding new ids.
   typedef base::Callback<void(bool)> AddResultCallback;