Skip groups properly.

Now the generated code doesn't need to check for end group tags, as it will skip whole groups at a time.
Currently it will ignore extraneous end group tags, which may or may not be a good thing.
Renamed ConsumeLastField to SkipLastField as it felt more natural.
Removed WireFormat.IsEndGroupTag as it's no longer useful.

This mostly fixes issue 688.

(Generated code changes coming in next commit.)

1 files changed, 2 insertions, 3 deletions

diff --git a/csharp/src/Google.Protobuf/Collections/MapField.cs b/csharp/src/Google.Protobuf/Collections/MapField.cs
index 5eb2c2fc..dc4b04cb 100644
--- a/csharp/src/Google.Protobuf/Collections/MapField.cs
+++ b/csharp/src/Google.Protobuf/Collections/MapField.cs
@@ -637,10 +637,9 @@ namespace Google.Protobuf.Collections
                         {
                             Value = codec.valueCodec.Read(input);
                         }
-                        else if (WireFormat.IsEndGroupTag(tag))
+                        else 
                         {
-                            // TODO(jonskeet): Do we need this? (Given that we don't support groups...)
-                            return;
+                            input.SkipLastField();
                         }
                     }
                 }