Slightly simplify building FillLayer objects

Source/build/scripts/templates/StyleBuilderFunctions.cpp.tmpl

 {% from 'macros.tmpl' import license %}
 {#
     This file is for property handlers which use the templating engine to
     reduce (handwritten) code duplication.
 
     The `properties' dict can be used to access a property's parameters in
     jinja2 templates (i.e. setter, getter, initial, type_name)
 #}
 #include "config.h"
 #include "StyleBuilderFunctions.h"
@@ skipping 382 matching lines @@
     for (currChild = currChild->next(); currChild; currChild = currChild->next())
         currChild->clear{{fill_type}}();
 }
 
 {{declare_inherit_function(property_id)}}
 {
     FillLayer* currChild = &state.style()->{{access_layers}}();
     FillLayer* prevChild = 0;
     const FillLayer* currParent = &state.parentStyle()->{{layer_type|lower}}Layers();
     while (currParent && currParent->is{{fill_type}}Set()) {
-        if (!currChild) {
-            /* Need to make a new layer.*/
-            currChild = new FillLayer({{fill_layer_type}});
-            prevChild->setNext(currChild);
-        }
+        if (!currChild)
+            currChild = prevChild->ensureNext();
         currChild->set{{fill_type}}(currParent->{{fill_type|lower_first}}());
         prevChild = currChild;
         currChild = prevChild->next();
         currParent = currParent->next();
     }
 
     while (currChild) {
         /* Reset any remaining layers to not have the property set. */
         currChild->clear{{fill_type}}();
         currChild = currChild->next();
     }
 }
 
 {{declare_value_function(property_id)}}
 {
     FillLayer* currChild = &state.style()->{{access_layers}}();
     FillLayer* prevChild = 0;
     if (value->isValueList() && !value->isImageSetValue()) {
         /* Walk each value and put it into a layer, creating new layers as needed. */
         CSSValueList* valueList = toCSSValueList(value);
         for (unsigned int i = 0; i < valueList->length(); i++) {
-            if (!currChild) {
-                /* Need to make a new layer to hold this value */
-                currChild = new FillLayer({{fill_layer_type}});
-                prevChild->setNext(currChild);
-            }
+            if (!currChild)
+                currChild = prevChild->ensureNext();
             state.styleMap().{{map_fill}}({{property_id}}, currChild, valueList->item(i));
             prevChild = currChild;
             currChild = currChild->next();
         }
     } else {
         state.styleMap().{{map_fill}}({{property_id}}, currChild, value);
         currChild = currChild->next();
     }
     while (currChild) {
         /* Reset all remaining layers to not have the property set. */
@@ skipping 198 matching lines @@
         }
         {{set_value(property)}}(ptype, c, url,
             state.applyPropertyToRegularStyle(),
             state.applyPropertyToVisitedLinkStyle());
     }
 }
 {% endmacro %}
 {{apply_svg_paint('CSSPropertyFill', 'FillPaint')}}
 {{apply_svg_paint('CSSPropertyStroke', 'StrokePaint')}}
 } // namespace WebCore