Devirtualize LayoutBlock::firstLineBlock()

third_party/WebKit/Source/core/layout/LayoutObject.cpp

Index: third_party/WebKit/Source/core/layout/LayoutObject.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutObject.cpp b/third_party/WebKit/Source/core/layout/LayoutObject.cpp
index ff366cd2570eae7e854f1094a13c67f6d22a8fc7..b732c256628dfacd944b1363e34330675a5faf96 100644
--- a/third_party/WebKit/Source/core/layout/LayoutObject.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutObject.cpp
@@ -725,11 +725,6 @@ bool LayoutObject::skipInvalidationWhenLaidOutChildren() const
     return !hasBoxEffect();
 }
 
-LayoutBlock* LayoutObject::firstLineBlock() const
-{
-    return nullptr;
-}
-
 static inline bool objectIsRelayoutBoundary(const LayoutObject* object)
 {
     // FIXME: In future it may be possible to broaden these conditions in order to improve performance.
@@ -2822,7 +2817,7 @@ static PassRefPtr<ComputedStyle> firstLineStyleForCachedUncachedType(StyleCacheS
         layoutObjectForFirstLineStyle = layoutObject->parent();
 
     if (layoutObjectForFirstLineStyle->isLayoutBlockFlow() || layoutObjectForFirstLineStyle->isLayoutButton()) {
-        if (LayoutBlock* firstLineBlock = layoutObjectForFirstLineStyle->firstLineBlock()) {
+        if (LayoutBlock* firstLineBlock = toLayoutBlock(layoutObjectForFirstLineStyle)->firstLineBlock()) {
             if (type == Cached)
                 return firstLineBlock->getCachedPseudoStyle(FIRST_LINE, style);
             return firstLineBlock->getUncachedPseudoStyle(PseudoStyleRequest(FIRST_LINE), style, firstLineBlock == layoutObject ? style : 0);