[CSS Typed OM] Add CSSValue->CSSSkew conversions

third_party/WebKit/Source/core/css/cssom/CSSSkew.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/CSSSkew.h"
 
 #include "core/css/CSSFunctionValue.h"
 #include "core/css/CSSPrimitiveValue.h"
+#include "core/css/cssom/CSSAngleValue.h"
 
 namespace blink {
 
+CSSSkew* CSSSkew::fromCSSValue(const CSSFunctionValue& value) {
+  const CSSPrimitiveValue& xValue = toCSSPrimitiveValue(value.item(0));
+  if (xValue.isCalculated()) {
+    // TODO(meade): Decide what we want to do with calc angles.
+    return nullptr;
+  }
+  DCHECK(xValue.isAngle());
+  switch (value.functionType()) {
+    case CSSValueSkew:
+      if (value.length() == 2U) {
+        const CSSPrimitiveValue& yValue = toCSSPrimitiveValue(value.item(1));
+        if (yValue.isCalculated()) {
+          // TODO(meade): Decide what we want to do with calc angles.
+          return nullptr;
+        }
+        DCHECK(yValue.isAngle());
+        return CSSSkew::create(CSSAngleValue::fromCSSValue(xValue),
+                               CSSAngleValue::fromCSSValue(yValue));
+      }
+    // Else fall through; skew(ax) == skewX(ax).
+    case CSSValueSkewX:
+      DCHECK_EQ(value.length(), 1U);
+      return CSSSkew::create(
+          CSSAngleValue::fromCSSValue(xValue),
+          CSSAngleValue::create(0, CSSPrimitiveValue::UnitType::Degrees));
+    case CSSValueSkewY:
+      DCHECK_EQ(value.length(), 1U);
+      return CSSSkew::create(
+          CSSAngleValue::create(0, CSSPrimitiveValue::UnitType::Degrees),
+          CSSAngleValue::fromCSSValue(xValue));
+    default:
+      NOTREACHED();
+      return nullptr;
+  }
+}
+
 CSSFunctionValue* CSSSkew::toCSSValue() const {
   CSSFunctionValue* result = CSSFunctionValue::create(CSSValueSkew);
   result->append(*CSSPrimitiveValue::create(m_ax->value(), m_ax->unit()));
   result->append(*CSSPrimitiveValue::create(m_ay->value(), m_ay->unit()));
   return result;
 }
 
 }  // namespace blink