[CSS Typed OM] Make the attributes of CSSPerspective mutable.

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(CSSNumericValue* length,
                                        ExceptionState& exception_state) {
   if (length->GetType() != CSSStyleValue::StyleValueType::kLengthType) {
-    exception_state.ThrowTypeError("Must pass length to CSSNumericValue");
+    exception_state.ThrowTypeError("Must pass length to CSSPerspective");
     return nullptr;
   }
   if (length->ContainsPercent()) {
     exception_state.ThrowTypeError(
         "CSSPerspective does not support CSSNumericValues with percent units");
     return nullptr;
   }
   return new CSSPerspective(length);
 }
 
+void CSSPerspective::setLength(CSSNumericValue* length,
+                               ExceptionState& exception_state) {
+  if (length->GetType() != CSSStyleValue::StyleValueType::kLengthType) {
+    exception_state.ThrowTypeError("Must pass length to CSSPerspective");
+    return;
+  }
+  if (length->ContainsPercent()) {
+    exception_state.ThrowTypeError(
+        "CSSPerspective does not support CSSNumericValues with percent units");
+    return;
+  }
+  length_ = 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 {
   CSSFunctionValue* result = CSSFunctionValue::Create(CSSValuePerspective);
   result->Append(*length_->ToCSSValue());
   return result;
 }
 
 }  // namespace blink