Remove the remaining parts of ignorePendingStylesheets and placeholder styles.

sky/engine/core/rendering/style/RenderStyle.cpp

Index: sky/engine/core/rendering/style/RenderStyle.cpp
diff --git a/sky/engine/core/rendering/style/RenderStyle.cpp b/sky/engine/core/rendering/style/RenderStyle.cpp
index 8f5f7253ea73997ec0cac1f3b444b45812987d16..b131493481958b5cce8113b558097815abec1d6b 100644
--- a/sky/engine/core/rendering/style/RenderStyle.cpp
+++ b/sky/engine/core/rendering/style/RenderStyle.cpp
@@ -212,11 +212,6 @@ bool RenderStyle::operator==(const RenderStyle& o) const
         && inherited == o.inherited;
 }
 
-bool RenderStyle::isStyleAvailable() const
-{
-    return this != StyleResolver::styleNotYetAvailable();
-}
-
 bool RenderStyle::inheritedNotEqual(const RenderStyle* other) const
 {
     return inherited_flags != other->inherited_flags