Add metric name for MinVideoAndAudioBitRate.

It shouldn't be empty. As it was before it printed
  RESULT min_test_bitrate_no_allocation_strategy: = 80 kbps
Whereas now it prints
  RESULT min_test_bitrate_no_allocation_strategy: min_bitrate= 80 kbps

Bug: webrtc:7156
Change-Id: Ie86e3912d296d6d7bd6936d1709df9d2dc7fc143
Reviewed-on: https://webrtc-review.googlesource.com/38040
Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
Reviewed-by: Henrik Andreassson <henrika@webrtc.org>
Commit-Queue: Edward Lemur <ehmaldonado@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21529}
diff --git a/call/call_perf_tests.cc b/call/call_perf_tests.cc
index f0c781c..f457546 100644
--- a/call/call_perf_tests.cc
+++ b/call/call_perf_tests.cc
@@ -894,11 +894,11 @@
       }
       EXPECT_GT(last_passed_test_bitrate, -1)
           << "Minimum supported bitrate out of the test scope";
-      webrtc::test::PrintResult("min_test_bitrate_",
-                                use_bitrate_allocation_strategy_
-                                    ? "with_allocation_strategy"
-                                    : "no_allocation_strategy",
-                                "", last_passed_test_bitrate, "kbps", false);
+      webrtc::test::PrintResult(
+          "min_test_bitrate_",
+          use_bitrate_allocation_strategy_ ? "with_allocation_strategy"
+                                           : "no_allocation_strategy",
+          "min_bitrate", last_passed_test_bitrate, "kbps", false);
     }
 
     void OnCallsCreated(Call* sender_call, Call* receiver_call) override {