Remove CSS.unregisterProperty as the WG resolved to remove it for now

third_party/WebKit/Source/core/css/PropertyRegistration.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/css/PropertyRegistration.h"
 
 #include "core/css/CSSSyntaxDescriptor.h"
 #include "core/css/CSSValueList.h"
 #include "core/css/CSSVariableReferenceValue.h"
 #include "core/css/PropertyDescriptor.h"
@@ skipping 110 matching lines @@
     registry.registerProperty(atomicName, syntaxDescriptor,
                               descriptor.inherits(), nullptr, nullptr);
   }
 
   // TODO(timloh): Invalidate only elements with this custom property set
   document->setNeedsStyleRecalc(SubtreeStyleChange,
                                 StyleChangeReasonForTracing::create(
                                     StyleChangeReason::PropertyRegistration));
 }
 
-void PropertyRegistration::unregisterProperty(
-    ExecutionContext* executionContext,
-    const String& property,
-    ExceptionState& exceptionState) {
-  Document* document = toDocument(executionContext);
-  PropertyRegistry& registry = *document->propertyRegistry();
-  AtomicString atomicProperty(property);
-  if (!registry.registration(atomicProperty)) {
-    exceptionState.throwDOMException(
-        NotFoundError,
-        "CSS.unregisterProperty() called with non-registered property " +
-            property);
-    return;
-  }
-  registry.unregisterProperty(atomicProperty);
-
-  document->setNeedsStyleRecalc(SubtreeStyleChange,
-                                StyleChangeReasonForTracing::create(
-                                    StyleChangeReason::PropertyUnregistration));
-}
-
 }  // namespace blink