Add propagation of test duration to PC framework user.

Add method to get real test execution time, where test execution time is
time from call setup to call terminated.

Bug: webrtc:10138
Change-Id: I7ae3995c0051ecb4fc796b895be1180c8aab77cf
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/134302
Commit-Queue: Artem Titov <titovartem@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Bjorn Mellem <mellem@webrtc.org>
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27822}

api/test/peerconnection_quality_test_fixture.h

@@ -237,6 +237,13 @@ class PeerConnectionE2EQualityTestFixture {
                        rtc::NetworkManager* network_manager,
                        rtc::FunctionView<void(PeerConfigurer*)> configurer) = 0;
   virtual void Run(RunParams run_params) = 0;
+
+  // Returns real test duration - the time of test execution measured during
+  // test. Client must call this method only after test is finished (after
+  // Run(...) method returned). Test execution time is time from end of call
+  // setup (offer/answer, ICE candidates exchange done and ICE connected) to
+  // start of call tear down (PeerConnection closed).
+  virtual TimeDelta GetRealTestDuration() const = 0;
 };
 
 }  // namespace webrtc_pc_e2e