Change DontCheck under-invalidation checking mode to CacheSkipper

Source/platform/graphics/paint/DrawingDisplayItem.h

 // Copyright 2014 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.
 
 #ifndef DrawingDisplayItem_h
 #define DrawingDisplayItem_h
 
 #include "platform/PlatformExport.h"
 #include "platform/geometry/FloatPoint.h"
 #include "platform/graphics/paint/DisplayItem.h"
 #include "third_party/skia/include/core/SkPicture.h"
 #include "wtf/PassOwnPtr.h"
 
 namespace blink {
 
 class PLATFORM_EXPORT DrawingDisplayItem : public DisplayItem {
 public:
 #if ENABLE(ASSERT)
     enum UnderInvalidationCheckingMode {
         CheckPicture, // Check if the new picture and the old picture are the same
         CheckBitmap, // Check if the new picture and the old picture produce the same bitmap
-        DontCheck // Skip for known bugs. Each usage should have a FIXME and a link to the bug.
     };
 #endif
 
     DrawingDisplayItem(const DisplayItemClientWrapper& client, Type type, PassRefPtr<const SkPicture> picture)
         : DisplayItem(client, type)
         , m_picture(picture && picture->approximateOpCount() ? picture : nullptr)
 #if ENABLE(ASSERT)
         , m_underInvalidationCheckingMode(CheckPicture)
 #endif
     {
@@ skipping 24 matching lines @@
     RefPtr<const SkPicture> m_picture;
 
 #if ENABLE(ASSERT)
     UnderInvalidationCheckingMode m_underInvalidationCheckingMode;
 #endif
 };
 
 } // namespace blink
 
 #endif // DrawingDisplayItem_h