Remove untrusted event deprecation warning.

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"
 #include "core/frame/LocalFrame.h"
 #include "core/inspector/ConsoleMessage.h"
 #include "core/workers/WorkerGlobalScope.h"
 
 namespace {
 
 enum Milestone {
-    M53,
     M55,
     M56,
     M57,
     M58,
     M59,
 };
 
 const char* milestoneString(Milestone milestone)
 {
     // These are the Estimated Stable Dates:
     // https://www.chromium.org/developers/calendar
 
     switch (milestone) {
-    case M53:
-        return "M53, around September 2016";
     case M55:
         return "M55, around December 2016";
     case M56:
         return "M56, around January 2017";
     case M57:
         return "M57, around March 2017";
     case M58:
         return "M58, around April 2017";
     case M59:
         return "M59, around June 2017";
@@ skipping 311 matching lines @@
 
     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");
 
     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::UntrustedEventDefaultHandled:
-        return String::format("A DOM event generated from JavaScript has triggered a default action inside the browser. This behavior is non-standard and will be removed in %s. See https://www.chromestatus.com/features/5718803933560832 for more details.", milestoneString(M53));
-
     case UseCounter::TouchStartUserGestureUtilized:
         return willBeRemoved("Performing operations that require explicit user interaction on touchstart events", M55, "5649871251963904");
 
     case UseCounter::TouchMoveUserGestureUtilized:
         return willBeRemoved("Performing operations that require explicit user interaction on touchmove events", M55, "5649871251963904");
 
     case UseCounter::TouchEndDuringScrollUserGestureUtilized:
         return willBeRemoved("Performing operations that require explicit user interaction on touchend events that occur as part of a scroll", M55, "5649871251963904");
 
     case UseCounter::MIDIMessageEventReceivedTime:
@@ skipping 22 matching lines @@
     case UseCounter::PaymentAddressCareOf:
         return willBeRemoved("PaymentAddress.careOf", M56, "5728579069411328");
 
     // Features that aren't deprecated don't have a deprecation message.
     default:
         return String();
     }
 }
 
 } // namespace blink