Remove Object.observe UseCounter and 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"
@@ skipping 325 matching lines @@
 
     case UseCounter::PrefixedPerformanceResourceTimingBufferFull:
         return replacedBy("'Performance.onwebkitresourcetimingbufferfull'", "'Performance.onresourcetimingbufferfull'");
 
     case UseCounter::MediaStreamTrackGetSources:
         return "MediaStreamTrack.getSources is deprecated. See https://www.chromestatus.com/feature/4765305641369600 for more details.";
 
     case UseCounter::V8TouchEvent_InitTouchEvent_Method:
         return replacedWillBeRemoved("'TouchEvent.initTouchEvent'", "the TouchEvent constructor", 53, "5730982598541312");
 
-    case UseCounter::ObjectObserve:
-        return willBeRemoved("'Object.observe'", 50, "6147094632988672");
-
     case UseCounter::SVGZoomEvent:
         return willBeRemoved("'SVGZoomEvent'", 52, "5760883808534528");
 
     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", 54, "5716060992962560");
 
     case UseCounter::WebAnimationsEasingAsFunctionLinear:
@@ skipping 32 matching lines @@
     case UseCounter::MIDIMessageEventReceivedTime:
         return willBeRemoved("MIDIMessageEvent.receivedTime", 56, "5665772797952000");
 
     // Features that aren't deprecated don't have a deprecation message.
     default:
         return String();
     }
 }
 
 } // namespace blink