Fix compile failure in Deprecation.cpp (missing M60 enum value)

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/WorkerOrWorkletGlobalScope.h"
 
 namespace {
 
 enum Milestone {
   M56,
   M57,
   M58,
   M59,
+  M60,
 };
 
 const char* milestoneString(Milestone milestone) {
   // These are the Estimated Stable Dates:
   // https://www.chromium.org/developers/calendar
 
   switch (milestone) {
     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";
+    case M60:
+      return "M60, around August 2017";
   }
 
   ASSERT_NOT_REACHED();
   return nullptr;
 }
 
 String replacedBy(const char* feature, const char* replacement) {
   return String::format("%s is deprecated. Please use %s instead.", feature,
                         replacement);
 }
@@ skipping 401 matching lines @@
           "for more details.",
           milestoneString(M60));
 
     // Features that aren't deprecated don't have a deprecation message.
     default:
       return String();
   }
 }
 
 }  // namespace blink