Pass around the candidate removals events in IOS clients

webrtc/examples/objc/AppRTCDemo/ARDSignalingMessage.m

Index: webrtc/examples/objc/AppRTCDemo/ARDSignalingMessage.m
diff --git a/webrtc/examples/objc/AppRTCDemo/ARDSignalingMessage.m b/webrtc/examples/objc/AppRTCDemo/ARDSignalingMessage.m
index a5ca29576a0c0315194b00b938efc98e26d3be04..1a30fb37d777e53d371175f61ab5d5bfea582450 100644
--- a/webrtc/examples/objc/AppRTCDemo/ARDSignalingMessage.m
+++ b/webrtc/examples/objc/AppRTCDemo/ARDSignalingMessage.m
@@ -17,6 +17,7 @@
 #import "RTCSessionDescription+JSON.h"
 
 static NSString const *kARDSignalingMessageTypeKey = @"type";
+static NSString const *kARDSignalingMessageCandidatesKey = @"candidates";
 
 @implementation ARDSignalingMessage
 
@@ -47,6 +48,18 @@ static NSString const *kARDSignalingMessageTypeKey = @"type";
     RTCIceCandidate *candidate =
         [RTCIceCandidate candidateFromJSONDictionary:values];
     message = [[ARDICECandidateMessage alloc] initWithCandidate:candidate];
+  } else if ([typeString isEqualToString:@"remove-candidates"]) {
+    RTCLogInfo(@"Received remove-candidates message");
+    NSArray *jsonCandidates = values[kARDSignalingMessageCandidatesKey];
+    NSMutableArray<RTCIceCandidate *> *candidates =
+        [NSMutableArray arrayWithCapacity:jsonCandidates.count];
+    for (NSDictionary *jsonCandidate in jsonCandidates) {
+      RTCIceCandidate *candidate =
+          [RTCIceCandidate candidateFromJSONDictionary:jsonCandidate];
+      [candidates addObject:candidate];
+    }
+    message = [[ARDICECandidatesRemovalMessage alloc]
+                  initWithRemovedCandidates:candidates];
   } else if ([typeString isEqualToString:@"offer"] ||
              [typeString isEqualToString:@"answer"]) {
     RTCSessionDescription *description =
@@ -84,6 +97,44 @@ static NSString const *kARDSignalingMessageTypeKey = @"type";
 
 @end
 
+@implementation ARDICECandidatesRemovalMessage
+
+@synthesize candidates = _candidates;
+
+- (instancetype)initWithRemovedCandidates:(
+    NSArray<RTCIceCandidate *> *)candidates {
+  NSParameterAssert(candidates.count);
+  if (self = [super initWithType:kARDSignalingMessageTypeCandidatesRemoval]) {
+    _candidates = candidates;
+  }
+  return self;
+}
+
+- (NSData *)JSONData {
+  NSMutableArray *jsonCandidates =
+      [NSMutableArray arrayWithCapacity:_candidates.count];
+  for (RTCIceCandidate *candidate in _candidates) {
+    NSDictionary *jsonCandidate = [candidate JSONDictionary];
+    [jsonCandidates addObject:jsonCandidate];
+  }
+  NSDictionary *json = @{
+    kARDSignalingMessageTypeKey : @"remove-candidates",
+    kARDSignalingMessageCandidatesKey : jsonCandidates
+  };
+  NSError *error = nil;
+  NSData *data =
+      [NSJSONSerialization dataWithJSONObject:json
+                                      options:NSJSONWritingPrettyPrinted
+                                        error:&error];
+  if (error) {
+    RTCLogError(@"Error serializing JSON: %@", error);
+    return nil;
+  }
+  return data;
+}
+
+@end
+
 @implementation ARDSessionDescriptionMessage
 
 @synthesize sessionDescription = _sessionDescription;