Throw TypeError if easing string is invalid.

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 352 matching lines @@
 
     case UseCounter::HTMLKeygenElement:
         return willBeRemoved("The <keygen> element", 54, "5716060992962560");
 
     case UseCounter::ResultsAttribute:
         return willBeRemoved("'results' attribute", 53, "5738199536107520");
 
     case UseCounter::TouchDragUserGestureUsedCrossOrigin:
         return willBeRemoved("Performing sensitive operations in iframes on touch events which don't represent a tap gesture", 52, "https://www.chromestatus.com/features/5649871251963904");
 
+    case UseCounter::WebAnimationsEasingAsFunctionLinear:
+        return String::format("Specifying animation easing as a function is deprecated and all support will be removed in %s, at which point this will throw a TypeError. This warning may have been triggered by the Web Animations or Polymer polyfills. See http://crbug.com/601672 for details.", milestoneString(54));
+
     // Features that aren't deprecated don't have a deprecation message.
     default:
         return String();
     }
 }
 
 } // namespace blink