Let PrintResultMeanAndError accept a string.

Some downstream projects still use it. I'll update them and then revert
this change.

Bug: webrtc:8566
Change-Id: Ib4e56348c40a3645f3049382b47089ca6c675e96
Reviewed-on: https://webrtc-review.googlesource.com/25841
Commit-Queue: Edward Lemur <ehmaldonado@webrtc.org>
Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20872}
diff --git a/test/testsupport/perf_test.cc b/test/testsupport/perf_test.cc
index bb4491a..cf244df 100644
--- a/test/testsupport/perf_test.cc
+++ b/test/testsupport/perf_test.cc
@@ -85,6 +85,16 @@
                    units, important);
 }
 
+void PrintResultMeanAndError(const std::string& measurement,
+                             const std::string& modifier,
+                             const std::string& trace,
+                             const std::string& mean_and_error,
+                             const std::string& units,
+                             bool important) {
+  PrintResultsImpl(measurement, modifier, trace, mean_and_error, "{", "}",
+                   units, important);
+}
+
 void PrintResultList(const std::string& measurement,
                      const std::string& modifier,
                      const std::string& trace,
diff --git a/test/testsupport/perf_test.h b/test/testsupport/perf_test.h
index 02dd1f3..2c98b8e 100644
--- a/test/testsupport/perf_test.h
+++ b/test/testsupport/perf_test.h
@@ -52,6 +52,13 @@
                              const std::string& units,
                              bool important);
 
+void PrintResultMeanAndError(const std::string& measurement,
+                             const std::string& modifier,
+                             const std::string& trace,
+                             const std::string& mean_and_error,
+                             const std::string& units,
+                             bool important);
+
 // Like PrintResult(), but prints an entire list of results. The |values|
 // will generally be a list of comma-separated numbers. A typical
 // post-processing step might produce plots of their mean and standard