Adding Deprecation Message for <keygen>

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

Index: third_party/WebKit/Source/core/frame/UseCounter.cpp
diff --git a/third_party/WebKit/Source/core/frame/UseCounter.cpp b/third_party/WebKit/Source/core/frame/UseCounter.cpp
index 7e3cb26b7cad64122aa4a40c34fb1e8a773b8c92..29fda259c42ea387890b2b34f706b22bd75e5002 100644
--- a/third_party/WebKit/Source/core/frame/UseCounter.cpp
+++ b/third_party/WebKit/Source/core/frame/UseCounter.cpp
@@ -749,6 +749,8 @@ static const char* milestoneString(int milestone)
         return "M50, around April 2016";
     case 53:
         return "M53, around September 2016";
+    case 54:
+        return "M54, around October 2016";
     }
 
     ASSERT_NOT_REACHED();
@@ -986,6 +988,9 @@ String UseCounter::deprecationMessage(Feature feature)
     case NonCSSStyleSheetType:
         return String::format("Using stylesheet links with types other than 'text/css' is deprecated and will be removed in %s.", milestoneString(50));
 
+    case HTMLKeygenElement:
+        return willBeRemoved("The <keygen> element", 54, "5716060992962560");
+
     // Features that aren't deprecated don't have a deprecation message.
     default:
         return String();