Updating deprecation message for <keygen>.

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

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/frame/Deprecation.h"
 
 #include "core/dom/Document.h"
 #include "core/dom/ExecutionContext.h"
 #include "core/frame/FrameConsole.h"
 #include "core/frame/FrameHost.h"
@@ skipping 389 matching lines @@
 
     case UseCounter::PrefixedPerformanceResourceTimingBufferFull:
       return replacedBy("'Performance.onwebkitresourcetimingbufferfull'",
                         "'Performance.onresourcetimingbufferfull'");
 
     case UseCounter::WebAnimationHyphenatedProperty:
       return "Hyphenated property names in Web Animations keyframes are "
              "invalid and therefore ignored. Please use camelCase instead.";
 
     case UseCounter::HTMLKeygenElement:
-      return willBeRemoved("The <keygen> element", M56, "5716060992962560");
+      return willBeRemoved("The <keygen> element", M57, "5716060992962560");
 
     case UseCounter::EncryptedMediaAllSelectedContentTypesMissingCodecs:
       return String::format(
           "EME requires that contentType strings accepted by "
           "requestMediaKeySystemAccess() include codecs. Non-standard support "
           "for contentType strings without codecs will be removed in %s. "
           "Please specify the desired codec(s) as part of the contentType.",
           milestoneString(M56));
 
     case UseCounter::MIDIMessageEventReceivedTime:
@@ skipping 24 matching lines @@
     case UseCounter::VRDeprecatedGetPose:
       return replacedBy("VRDisplay.getPose()", "VRDisplay.getFrameData()");
 
     // Features that aren't deprecated don't have a deprecation message.
     default:
       return String();
   }
 }
 
 }  // namespace blink