Add UMA metrics for ICE regathering reasons.

webrtc/p2p/client/basicportallocator.cc

Index: webrtc/p2p/client/basicportallocator.cc
diff --git a/webrtc/p2p/client/basicportallocator.cc b/webrtc/p2p/client/basicportallocator.cc
index dba68f177e5120a496a39d603d622971ac776ac4..237c649beaa47c8194677e4767b8dd3f60cff784 100644
--- a/webrtc/p2p/client/basicportallocator.cc
+++ b/webrtc/p2p/client/basicportallocator.cc
@@ -14,6 +14,7 @@
 #include <string>
 #include <vector>
 
+#include "webrtc/api/peerconnectioninterface.h"
 #include "webrtc/p2p/base/basicpacketsocketfactory.h"
 #include "webrtc/p2p/base/common.h"
 #include "webrtc/p2p/base/port.h"
@@ -156,8 +157,11 @@ BasicPortAllocator::~BasicPortAllocator() {
 PortAllocatorSession* BasicPortAllocator::CreateSessionInternal(
     const std::string& content_name, int component,
     const std::string& ice_ufrag, const std::string& ice_pwd) {
-  return new BasicPortAllocatorSession(
+  PortAllocatorSession* session = new BasicPortAllocatorSession(
       this, content_name, component, ice_ufrag, ice_pwd);
+  session->SignalIceRegatheringReason.connect(
+      this, &BasicPortAllocator::ReportIceRegatheringReason);
+  return session;
 }
 
 void BasicPortAllocator::AddTurnServer(const RelayServerConfig& turn_server) {
@@ -167,6 +171,15 @@ void BasicPortAllocator::AddTurnServer(const RelayServerConfig& turn_server) {
                    prune_turn_ports());
 }
 
+void BasicPortAllocator::ReportIceRegatheringReason(

[pthatcher2, 2016/10/04 06:03:17]

Similarly, I think calling this ReportIceRegathering would make more sense.

[honghaiz3, 2016/10/05 05:01:53]

This method is removed.

+    IceRegatheringReason reason) {
+  if (metrics_observer()) {
+    metrics_observer()->IncrementEnumCounter(
+        webrtc::kEnumCounterIceRegatheringReason, static_cast<int>(reason),
+        static_cast<int>(IceRegatheringReason::MAX_VALUE));
+  }
+}
+
 // BasicPortAllocatorSession
 BasicPortAllocatorSession::BasicPortAllocatorSession(
     BasicPortAllocator* allocator,
@@ -247,7 +260,7 @@ void BasicPortAllocatorSession::StartGettingPorts() {
 
   network_thread_->Post(RTC_FROM_HERE, this, MSG_CONFIG_START);
 
-  LOG(LS_INFO) << "Pruning turn ports "
+  LOG(LS_INFO) << "Start getting ports with prune_turn_ports "
                << (prune_turn_ports_ ? "enabled" : "disabled");
 }
 
@@ -302,6 +315,8 @@ void BasicPortAllocatorSession::RegatherOnFailedNetworks() {
     return;
   }
 
+  LOG(LS_INFO) << "Regather candidates on failed networks";
+
   // Mark a sequence as "network failed" if its network is in the list of failed
   // networks, so that it won't be considered as equivalent when the session
   // regathers ports and candidates.
@@ -321,7 +336,10 @@ void BasicPortAllocatorSession::RegatherOnFailedNetworks() {
     PrunePortsAndRemoveCandidates(ports_to_prune);
   }
 
-  if (allocation_started_ && network_manager_started_) {
+  if (allocation_started_ && network_manager_started_ && !IsStopped()) {
+    SignalIceRegatheringReason(
+        IceRegatheringReason::CONTINUAL_GATHERING_BY_NETWORK_FAILURE);

[pthatcher2, 2016/10/04 06:03:17]

Actually, this makes it feel like we have two different stats:  ICE restarts and
ICE regatherings, which are not the same thing.  The ICE restarts can be
recorded by the IceTransport (P2pTransportChannel) and the ICE regatherings can
be recorded by the IceGatherer (PortAllocator).
2 different stats for 2 different things.

I think that would make the stats more clear and keep the relationship between
the IceTransport and IceGatherer more clear, which would address Taylor's
concern.

[honghaiz3, 2016/10/05 05:01:53]

Done.

+
     DoAllocate();
   }
 }
@@ -501,7 +519,7 @@ void BasicPortAllocatorSession::AllocatePorts() {
 }
 
 void BasicPortAllocatorSession::OnAllocate() {
-  if (network_manager_started_)
+  if (network_manager_started_ && !IsStopped())
     DoAllocate();
 
   allocation_started_ = true;
@@ -553,10 +571,6 @@ std::vector<rtc::Network*> BasicPortAllocatorSession::GetNetworks() {
 void BasicPortAllocatorSession::DoAllocate() {
   bool done_signal_needed = false;
   std::vector<rtc::Network*> networks = GetNetworks();
-
-  if (IsStopped()) {
-    return;
-  }
   if (networks.empty()) {
     LOG(LS_WARNING) << "Machine has no networks; no ports will be allocated";
     done_signal_needed = true;
@@ -627,12 +641,19 @@ void BasicPortAllocatorSession::OnNetworksChanged() {
     PrunePortsAndRemoveCandidates(ports_to_prune);
   }
 
+  if (allocation_started_ && !IsStopped()) {
+    if (network_manager_started_) {
+      // If the network manager has started, it must be a regathering.
+      SignalIceRegatheringReason(
+          IceRegatheringReason::CONTINUAL_GATHERING_BY_NETWORK_CHANGE);
+    }
+    DoAllocate();
+  }
+
   if (!network_manager_started_) {
-    LOG(LS_INFO) << "Network manager is started";
+    LOG(LS_INFO) << "Network manager has started";
     network_manager_started_ = true;
   }
-  if (allocation_started_)
-    DoAllocate();
 }
 
 void BasicPortAllocatorSession::DisableEquivalentPhases(