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

third_party/WebKit/Source/core/css/cssom/CSSPerspective.cpp

Index: third_party/WebKit/Source/core/css/cssom/CSSPerspective.cpp
diff --git a/third_party/WebKit/Source/core/css/cssom/CSSPerspective.cpp b/third_party/WebKit/Source/core/css/cssom/CSSPerspective.cpp
index 0cfda4436e14cb27569f8cad4bfa26b9600473f9..d32ad93aeca241ca2fca041782645952701ae1d6 100644
--- a/third_party/WebKit/Source/core/css/cssom/CSSPerspective.cpp
+++ b/third_party/WebKit/Source/core/css/cssom/CSSPerspective.cpp
@@ -11,7 +11,7 @@ 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()) {
@@ -22,6 +22,20 @@ CSSPerspective* CSSPerspective::Create(CSSNumericValue* length,
   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);