Introduce new constructor to PlatformThread.

webrtc/call/rampup_tests.h

Index: webrtc/call/rampup_tests.h
diff --git a/webrtc/call/rampup_tests.h b/webrtc/call/rampup_tests.h
index 65276ea265c820c37389ac947f4462332619a990..5ef5b2b80c0b7543684e1167e2002a1199991ca7 100644
--- a/webrtc/call/rampup_tests.h
+++ b/webrtc/call/rampup_tests.h
@@ -49,7 +49,7 @@ class RampUpTester : public test::EndToEndTest {
   void PerformTest() override;
 
  protected:
-  virtual bool PollStats();
+  virtual void PollStats();
 
   void AccumulateStats(const VideoSendStream::StreamStats& stream,
                        size_t* total_packets_sent,
@@ -95,7 +95,7 @@ class RampUpTester : public test::EndToEndTest {
       std::vector<FlexfecReceiveStream::Config>* receive_configs) override;
   void OnCallsCreated(Call* sender_call, Call* receiver_call) override;
 
-  static bool BitrateStatsPollingThread(void* obj);
+  static void BitrateStatsPollingThread(void* obj);
 
   const int start_bitrate_bps_;
   const int64_t min_run_time_ms_;
@@ -125,7 +125,7 @@ class RampUpDownUpTester : public RampUpTester {
   ~RampUpDownUpTester() override;
 
  protected:
-  bool PollStats() override;
+  void PollStats() override;
 
  private:
   enum TestStates {