Remove support for the keygen tag

third_party/WebKit/Source/core/frame/Deprecation.cpp

Index: third_party/WebKit/Source/core/frame/Deprecation.cpp
diff --git a/third_party/WebKit/Source/core/frame/Deprecation.cpp b/third_party/WebKit/Source/core/frame/Deprecation.cpp
index acd4a1ec5ee6789e01a315f9a3e05770479d27ef..f6de4d5f6e7e481326b30c4a86e3ec99b7bc5cc8 100644
--- a/third_party/WebKit/Source/core/frame/Deprecation.cpp
+++ b/third_party/WebKit/Source/core/frame/Deprecation.cpp
@@ -379,9 +379,6 @@ String Deprecation::deprecationMessage(UseCounter::Feature feature) {
       return replacedBy("'Performance.onwebkitresourcetimingbufferfull'",
                         "'Performance.onresourcetimingbufferfull'");
 
-    case UseCounter::HTMLKeygenElement:
-      return willBeRemoved("The <keygen> element", M57, "5716060992962560");
-
     case UseCounter::EncryptedMediaAllSelectedContentTypesMissingCodecs:
       return String::format(
           "EME requires that contentType strings accepted by "