Add instrumentation to track the IceEndpointType.

talk/app/webrtc/peerconnectioninterface.h

Index: talk/app/webrtc/peerconnectioninterface.h
diff --git a/talk/app/webrtc/peerconnectioninterface.h b/talk/app/webrtc/peerconnectioninterface.h
index ce32b50291a7a46c061bf36aabe9d7cf8d9096b2..27a81de290571a27c425e837b87b74e8f0fda980 100644
--- a/talk/app/webrtc/peerconnectioninterface.h
+++ b/talk/app/webrtc/peerconnectioninterface.h
@@ -124,7 +124,17 @@ class StatsObserver : public rtc::RefCountInterface {
 
 class MetricsObserverInterface : public rtc::RefCountInterface {
  public:
+  // TODO(guoweis): Remove this function once IncrementEnumCounter gets into
+  // chromium. IncrementCounter only deals with one type of enumeration counter,
+  // i.e. PeerConnectionMetricsCounter. Instead of creating a function for each
+  // enum type, IncrementEnumCounter is generalized with the enum type
+  // parameter.
   virtual void IncrementCounter(PeerConnectionMetricsCounter type) = 0;
+
+  virtual void IncrementEnumCounter(PeerConnectionEnumCounterType,
+                                    int enum_counter,
+                                    int enum_counter_max) {}
+
   virtual void AddHistogramSample(PeerConnectionMetricsName type,
                                   int value) = 0;
   // TODO(jbauch): Make method abstract when it is implemented by Chromium.
@@ -178,6 +188,8 @@ class PeerConnectionInterface : public rtc::RefCountInterface {
     kIceConnectionClosed,
   };
 
+  const int kIceConnectionState_Max = kIceConnectionClosed + 1;
+
   struct IceServer {
     // TODO(jbauch): Remove uri when all code using it has switched to urls.
     std::string uri;