Clean compositing inputs for location APIs for sticky-affected elements.

third_party/WebKit/Source/core/css/resolver/StyleBuilderCustom.cpp

Index: third_party/WebKit/Source/core/css/resolver/StyleBuilderCustom.cpp
diff --git a/third_party/WebKit/Source/core/css/resolver/StyleBuilderCustom.cpp b/third_party/WebKit/Source/core/css/resolver/StyleBuilderCustom.cpp
index b44925bed08f099a2ad791ae7fb6780cdcfc35e9..38515931c17f1dc4006c96b4eb4bf5ebafed77fc 100644
--- a/third_party/WebKit/Source/core/css/resolver/StyleBuilderCustom.cpp
+++ b/third_party/WebKit/Source/core/css/resolver/StyleBuilderCustom.cpp
@@ -966,10 +966,26 @@ void StyleBuilderFunctions::applyValueCSSPropertyBaselineShift(
   }
 }
 
+void StyleBuilderFunctions::applyInitialCSSPropertyPosition(
+    StyleResolverState& state) {
+  state.Style()->SetPosition(ComputedStyle::InitialPosition());
+  state.Style()->SetIsInStickySubtree(state.ParentStyle()->IsInStickySubtree());
+}
+
 void StyleBuilderFunctions::applyInheritCSSPropertyPosition(
     StyleResolverState& state) {
   if (!state.ParentNode()->IsDocumentNode())
     state.Style()->SetPosition(state.ParentStyle()->GetPosition());
+  state.Style()->SetIsInStickySubtree(state.ParentStyle()->IsInStickySubtree());
+}
+
+void StyleBuilderFunctions::applyValueCSSPropertyPosition(
+    StyleResolverState& state,
+    const CSSValue& value) {
+  EPosition position = ToCSSIdentifierValue(value).ConvertTo<EPosition>();
+  state.Style()->SetPosition(position);
+  state.Style()->SetIsInStickySubtree(position == EPosition::kSticky ||
+                                      state.ParentStyle()->IsInStickySubtree());
 }
 
 void StyleBuilderFunctions::applyInitialCSSPropertyCaretColor(