webkit: workaround incompatible operand types

Works around the following:
error: incompatible operand types ('WebCore::RenderStyle *' and 'bool')

Change-Id: Ic87e958d9bc06ce0a3ae203c8b4812d0e3a2aaef
diff --git a/Source/WebCore/dom/Element.cpp b/Source/WebCore/dom/Element.cpp
index 5fb6cdc..546671a 100644
--- a/Source/WebCore/dom/Element.cpp
+++ b/Source/WebCore/dom/Element.cpp
@@ -1073,7 +1073,7 @@
 {
     // Ref currentStyle in case it would otherwise be deleted when setRenderStyle() is called.
     RefPtr<RenderStyle> currentStyle(renderStyle());
-    bool hasParentStyle = parentNodeForRenderingAndStyle() ? parentNodeForRenderingAndStyle()->renderStyle() : false;
+    bool hasParentStyle = parentNodeForRenderingAndStyle() ? static_cast<bool>(parentNodeForRenderingAndStyle()->renderStyle()) : false;
     bool hasDirectAdjacentRules = currentStyle && currentStyle->childrenAffectedByDirectAdjacentRules();
 
     if ((change > NoChange || needsStyleRecalc())) {