Allow applications to limit the ICE check rate through RTCConfiguration

webrtc/p2p/base/p2ptransportchannel_unittest.cc

Index: webrtc/p2p/base/p2ptransportchannel_unittest.cc
diff --git a/webrtc/p2p/base/p2ptransportchannel_unittest.cc b/webrtc/p2p/base/p2ptransportchannel_unittest.cc
index b35bc1bbf97f06e50e393bfdf51d5ef7b9bc7420..82e6c019c64c45181a0a19a0bdbb7be8e76675e3 100644
--- a/webrtc/p2p/base/p2ptransportchannel_unittest.cc
+++ b/webrtc/p2p/base/p2ptransportchannel_unittest.cc
@@ -1217,7 +1217,7 @@ TEST_F(P2PTransportChannelTest, TestUMAIceRestartWhileDisconnected) {
 
   // Drop all packets so that both channels become not writable.
   fw()->AddRule(false, rtc::FP_ANY, rtc::FD_ANY, kPublicAddrs[0]);
-  const int kWriteTimeoutDelay = 6000;
+  const int kWriteTimeoutDelay = 8000;

[Taylor Brandstetter, 2017/02/02 07:03:55]

Why was this needed?

[skvlad, 2017/02/02 08:51:25]

The connection becomes FAILED when a certain set of conditions is met:
 - we have not received a ping response within CONNECTION_WRITE_CONNECT_TIMEOUT
(5 s)
 - there were at least CONNECTION_WRITE_CONNECT_FAILURES (5) failed pings
 - at least RTT has elapsed since the last ping was sent

The RTT estimation was capped at 3000 ms (actually 3000/2, because of this line:
https://cs.chromium.org/chromium/src/third_party/webrtc/p2p/base/port.cc?rcl=...
- that I couldn't find an explanation for). This CL changes the maximum RTT to
60 000 ms. The test results an RTT of 2250, that previously would be capped at
1500 and now (correctly) is not.

This increased the time it takes for this particular test to go to the FAILED
state from ~5500ms to ~7500ms (the state checks only happen when the next ping
is due to be sent). This made the 6000 ms timeout no longer sufficient.

Since the test is meant to verify UMA metrics and not ICE behavior, the exact
value of the timeout isn't essential - it needs to wait as long as necessary for
the state to become FAILED. However, increasing the (simulated) timeout is
sufficient in this case.

[Taylor Brandstetter, 2017/02/02 18:16:01]

Alright, makes sense.

   EXPECT_TRUE_SIMULATED_WAIT(!ep1_ch1()->writable() && !ep2_ch1()->writable(),
                              kWriteTimeoutDelay, clock);