Fix test bug introduced in r11101.

BUG=chromium:572995
R=pbos@webrtc.org

Review URL: https://codereview.webrtc.org/1578223002 .

Cr-Commit-Position: refs/heads/master@{#11224}
diff --git a/webrtc/call/rampup_tests.cc b/webrtc/call/rampup_tests.cc
index 9b31901..a3fcc30 100644
--- a/webrtc/call/rampup_tests.cc
+++ b/webrtc/call/rampup_tests.cc
@@ -87,6 +87,10 @@
   return send_transport_;
 }
 
+size_t RampUpTester::GetNumVideoStreams() const {
+  return num_video_streams_;
+}
+
 void RampUpTester::ModifyVideoConfigs(
     VideoSendStream::Config* send_config,
     std::vector<VideoReceiveStream::Config>* receive_configs,
diff --git a/webrtc/call/rampup_tests.h b/webrtc/call/rampup_tests.h
index d58470e..89e7075 100644
--- a/webrtc/call/rampup_tests.h
+++ b/webrtc/call/rampup_tests.h
@@ -39,6 +39,8 @@
                bool red);
   ~RampUpTester() override;
 
+  size_t GetNumVideoStreams() const override;
+
   void PerformTest() override;
 
  protected: