Add UMA for ICE restart states and ICE regathering reasons.

BUG=webrtc:6462

Review-Url: https://codereview.chromium.org/2444113002
Cr-Commit-Position: refs/heads/master@{#427230}

content/renderer/media/rtc_peer_connection_handler.cc

@@ -746,6 +746,14 @@ class PeerConnectionUMAObserver : public webrtc::UMAObserver {
         UMA_HISTOGRAM_ENUMERATION("WebRTC.PeerConnection.DtlsHandshakeError",
                                   counter, counter_max);
         break;
+      case webrtc::kEnumCounterIceRestart:
+        UMA_HISTOGRAM_ENUMERATION("WebRTC.PeerConnection.IceRestartState",
+                                  counter, counter_max);
+        break;
+      case webrtc::kEnumCounterIceRegathering:
+        UMA_HISTOGRAM_ENUMERATION("WebRTC.PeerConnection.IceRegatheringReason",
+                                  counter, counter_max);
+        break;
       default:
         // The default clause is expected to reach when new enum types are
         // added.

tools/metrics/histograms/histograms.xml

@@ -70677,6 +70677,19 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="WebRTC.PeerConnection.IceRegatheringReason"
+    enum="IceRegatheringReason">
+  <owner>honghaiz@chromium.org</owner>
+  <summary>Records the reasons for ICE re-gathering.</summary>
+</histogram>
+
+<histogram name="WebRTC.PeerConnection.IceRestartState" enum="IceRestartState">
+  <owner>honghaiz@chromium.org</owner>
+  <summary>
+    Records the transport channel states when ICE restart happens.
+  </summary>
+</histogram>
+
 <histogram name="WebRTC.PeerConnection.IPMetrics" enum="PeerConnectionCounters">
   <owner>mallinath@chromium.org</owner>
   <summary>
@@ -87364,6 +87377,17 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="6" label="IceconnectionClosed"/>
 </enum>
 
+<enum name="IceRegatheringReason" type="int">
+  <int value="0" label="NetworkChange"/>
+  <int value="1" label="NetworkFailure"/>
+</enum>
+
+<enum name="IceRestartState" type="int">
+  <int value="0" label="Connecting"/>
+  <int value="1" label="Connected"/>
+  <int value="2" label="Disconnected"/>
+</enum>
+
 <enum name="IDBContextForcedCloseReason" type="int">
   <int value="0" label="DeleteOrigin">
     A request was made to delete the data for an origin.