Remove candidates when doing continual gathering

talk/app/webrtc/jsepicecandidate.cc

Index: talk/app/webrtc/jsepicecandidate.cc
diff --git a/talk/app/webrtc/jsepicecandidate.cc b/talk/app/webrtc/jsepicecandidate.cc
index 768bd0a281bc3ee7097a116f00e3e4cc677c8644..2ca7ab134c74399d2304d69d34c1d3c490ce3101 100644
--- a/talk/app/webrtc/jsepicecandidate.cc
+++ b/talk/app/webrtc/jsepicecandidate.cc
@@ -96,4 +96,15 @@ bool JsepCandidateCollection::HasCandidate(
   return ret;
 }
 
+int JsepCandidateCollection::remove(const IceCandidateInterface* target) {
+  size_t original_size = candidates_.size();
+  auto new_end = std::remove_if(
+      candidates_.begin(), candidates_.end(),
+      [target](JsepIceCandidate* candidate) {
+        return target->candidate().IsWeaklyEquivalent(candidate->candidate());
+      });
+  candidates_.erase(new_end, candidates_.end());
+  return candidates_.size() - original_size;
+}
+
 }  // namespace webrtc