Reland the CL to remove candidates when doing continual gathering

webrtc/api/peerconnectioninterface.h

Index: webrtc/api/peerconnectioninterface.h
diff --git a/webrtc/api/peerconnectioninterface.h b/webrtc/api/peerconnectioninterface.h
index f6c8cbaf00bd0d93b2b7c60cd13506928b9a9de5..22109c4088e9415f0f55015ee95b9747dea24b4d 100644
--- a/webrtc/api/peerconnectioninterface.h
+++ b/webrtc/api/peerconnectioninterface.h
@@ -439,6 +439,12 @@ class PeerConnectionInterface : public rtc::RefCountInterface {
   // take the ownership of the |candidate|.
   virtual bool AddIceCandidate(const IceCandidateInterface* candidate) = 0;
 
+  // Removes a group of remote candidates from the ICE agent.
+  virtual bool RemoveIceCandidates(
+      const std::vector<cricket::Candidate>& candidates) {
+    return false;
+  }
+
   virtual void RegisterUMAObserver(UMAObserver* observer) = 0;
 
   // Returns the current SignalingState.
@@ -495,6 +501,12 @@ class PeerConnectionObserver {
   // New Ice candidate have been found.
   virtual void OnIceCandidate(const IceCandidateInterface* candidate) = 0;
 
+  // Ice candidates have been removed.
+  // TODO(honghaiz): Make this a pure virtual method when all its subclasses
+  // implement it.
+  virtual void OnIceCandidatesRemoved(
+      const std::vector<cricket::Candidate>& candidates) {}
+
   // Called when the ICE connection receiving status changes.
   virtual void OnIceConnectionReceivingChange(bool receiving) {}