Send the value of google_brand::GetBrand in component update checks.

components/update_client/utils.h

Index: components/update_client/utils.h
diff --git a/components/update_client/utils.h b/components/update_client/utils.h
index 80b7e071875f4d47913cf4760aa5f33983d898ec..bd428cafabdd441453c84334c7597c4c56d196d4 100644
--- a/components/update_client/utils.h
+++ b/components/update_client/utils.h
@@ -95,6 +95,9 @@ std::string GetCrxComponentID(const CrxComponent& component);
 bool VerifyFileHash256(const base::FilePath& filepath,
                        const std::string& expected_hash);
 
+// Returns true if the |brand| parameter matches ^([a-zA-Z]{4})?$ .
+bool IsValidBrand(const std::string& brand);
+
 }  // namespace update_client
 
 #endif  // COMPONENTS_UPDATE_CLIENT_UTILS_H_