Restructure type tracking in StyleValues to work better with new numeric types

third_party/WebKit/Source/core/css/cssom/CSSPerspective.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/cssom/CSSPerspective.h"
 
 #include "bindings/core/v8/ExceptionState.h"
 
 namespace blink {
 
 CSSPerspective* CSSPerspective::Create(const CSSNumericValue* length,
                                        ExceptionState& exception_state) {
   if (length->ContainsPercent()) {
     exception_state.ThrowTypeError(
         "CSSPerspective does not support CSSNumericValues with percent units");
     return nullptr;
   }
   return new CSSPerspective(length);
 }
 
 CSSPerspective* CSSPerspective::FromCSSValue(const CSSFunctionValue& value) {
   DCHECK_EQ(value.FunctionType(), CSSValuePerspective);
   DCHECK_EQ(value.length(), 1U);
   CSSNumericValue* length =
       CSSNumericValue::FromCSSValue(ToCSSPrimitiveValue(value.Item(0)));
+  // TODO(meade): This shouldn't happen once CSSNumericValue is fully
+  // implemented, so once that happens this check can be removed.
+  if (!length)
+    return nullptr;
   DCHECK(!length->ContainsPercent());
   return new CSSPerspective(length);
 }
 
 CSSFunctionValue* CSSPerspective::ToCSSValue() const {
-  return nullptr;
-  // CSSFunctionValue* result = CSSFunctionValue::Create(CSSValuePerspective);
-  // result->Append(*length_->ToCSSValue());
-  // return result;
+  CSSFunctionValue* result = CSSFunctionValue::Create(CSSValuePerspective);
+  result->Append(*length_->ToCSSValue());
+  return result;
 }
 
 }  // namespace blink