Factor out common BorderImageLength code in CSSToStyleMap

Source/core/css/CSSToStyleMap.cpp

Index: Source/core/css/CSSToStyleMap.cpp
diff --git a/Source/core/css/CSSToStyleMap.cpp b/Source/core/css/CSSToStyleMap.cpp
index 10530f487d080f296c199bb96fe74af669677dbe..eecea918e21133161adb170cd8abbf9f00bbc6c5 100644
--- a/Source/core/css/CSSToStyleMap.cpp
+++ b/Source/core/css/CSSToStyleMap.cpp
@@ -610,49 +610,31 @@ void CSSToStyleMap::mapNinePieceImageSlice(CSSValue* value, NinePieceImage& imag
     image.setFill(borderImageSlice->m_fill);
 }
 
+static BorderImageLength toBorderImageLength(CSSPrimitiveValue& value, const RenderStyle* currentStyle, const RenderStyle* rootStyle, float multiplier)
+{
+    if (value.isNumber())
+        return value.getDoubleValue();
+    if (value.isPercentage())
+        return Length(value.getDoubleValue(CSSPrimitiveValue::CSS_PERCENTAGE), Percent);
+    if (value.getValueID() != CSSValueAuto)
+        return value.computeLength<Length>(currentStyle, rootStyle, multiplier);
+    return Length(Auto);
+}
+
 BorderImageLengthBox CSSToStyleMap::mapNinePieceImageQuad(CSSValue* value) const
 {
     if (!value || !value->isPrimitiveValue())
-        return BorderImageLengthBox();
+        return BorderImageLengthBox(Length(Auto));
 
-    // Get our zoom value.
     float zoom = useSVGZoomRules() ? 1.0f : style()->effectiveZoom();
-
-    // Retrieve the primitive value.
-    CSSPrimitiveValue* borderWidths = toCSSPrimitiveValue(value);
-
-    // Set up a length box to represent our image slices.
-    BorderImageLengthBox box; // Defaults to 'auto' so we don't have to handle that explicitly below.
-    Quad* slices = borderWidths->getQuadValue();
-    if (slices->top()->isNumber())
-        box.setTop(slices->top()->getDoubleValue());
-    else if (slices->top()->isPercentage())
-        box.setTop(Length(slices->top()->getDoubleValue(CSSPrimitiveValue::CSS_PERCENTAGE), Percent));
-    else if (slices->top()->getValueID() != CSSValueAuto)
-        box.setTop(slices->top()->computeLength<Length>(style(), rootElementStyle(), zoom));
-
-    if (slices->right()->isNumber())
-        box.setRight(slices->right()->getDoubleValue());
-    else if (slices->right()->isPercentage())
-        box.setRight(Length(slices->right()->getDoubleValue(CSSPrimitiveValue::CSS_PERCENTAGE), Percent));
-    else if (slices->right()->getValueID() != CSSValueAuto)
-        box.setRight(slices->right()->computeLength<Length>(style(), rootElementStyle(), zoom));
-
-    if (slices->bottom()->isNumber())
-        box.setBottom(slices->bottom()->getDoubleValue());
-    else if (slices->bottom()->isPercentage())
-        box.setBottom(Length(slices->bottom()->getDoubleValue(CSSPrimitiveValue::CSS_PERCENTAGE), Percent));
-    else if (slices->bottom()->getValueID() != CSSValueAuto)
-        box.setBottom(slices->bottom()->computeLength<Length>(style(), rootElementStyle(), zoom));
-
-    if (slices->left()->isNumber())
-        box.setLeft(slices->left()->getDoubleValue());
-    else if (slices->left()->isPercentage())
-        box.setLeft(Length(slices->left()->getDoubleValue(CSSPrimitiveValue::CSS_PERCENTAGE), Percent));
-    else if (slices->left()->getValueID() != CSSValueAuto)
-        box.setLeft(slices->left()->computeLength<Length>(style(), rootElementStyle(), zoom));
-
-    return box;
+    Quad* slices = toCSSPrimitiveValue(value)->getQuadValue();
+
+    // Set up a border image length box to represent our image slices.
+    return BorderImageLengthBox(
+        toBorderImageLength(*slices->top(), style(), rootElementStyle(), zoom),
+        toBorderImageLength(*slices->right(), style(), rootElementStyle(), zoom),
+        toBorderImageLength(*slices->bottom(), style(), rootElementStyle(), zoom),
+        toBorderImageLength(*slices->left(), style(), rootElementStyle(), zoom));
 }
 
 void CSSToStyleMap::mapNinePieceImageRepeat(CSSValue* value, NinePieceImage& image) const