diff --git a/common/mock_http_fetcher.cc b/common/mock_http_fetcher.cc
index f3fa70d..d0348f1 100644
--- a/common/mock_http_fetcher.cc
+++ b/common/mock_http_fetcher.cc
@@ -20,6 +20,7 @@
 
 #include <base/bind.h>
 #include <base/logging.h>
+#include <base/strings/string_util.h>
 #include <base/time/time.h>
 #include <gtest/gtest.h>
 
@@ -117,6 +118,11 @@
   delegate_->TransferTerminated(this);
 }
 
+void MockHttpFetcher::SetHeader(const std::string& header_name,
+                                const std::string& header_value) {
+  extra_headers_[base::ToLowerASCII(header_name)] = header_value;
+}
+
 void MockHttpFetcher::Pause() {
   CHECK(!paused_);
   paused_ = true;