Make LayoutFlowThread::fragmentsBoundingBox() faster.

Source/core/layout/LayoutFlowThread.cpp

Index: Source/core/layout/LayoutFlowThread.cpp
diff --git a/Source/core/layout/LayoutFlowThread.cpp b/Source/core/layout/LayoutFlowThread.cpp
index 34e5d7793c5f95f03bd9b7239199d10e45d43fa7..91981f8a8d162d58a0b3661530f5ad645b5c2988 100644
--- a/Source/core/layout/LayoutFlowThread.cpp
+++ b/Source/core/layout/LayoutFlowThread.cpp
@@ -166,16 +166,8 @@ LayoutRect LayoutFlowThread::fragmentsBoundingBox(const LayoutRect& layerBoundin
     ASSERT(!m_columnSetsInvalidated);
 
     LayoutRect result;
-    for (auto* columnSet : m_multiColumnSetList) {
-        DeprecatedPaintLayerFragments fragments;
-        columnSet->collectLayerFragments(fragments, layerBoundingBox, LayoutRect(LayoutRect::infiniteIntRect()));
-        for (const auto& fragment : fragments) {
-            LayoutRect fragmentRect(layerBoundingBox);
-            fragmentRect.intersect(fragment.paginationClip);
-            fragmentRect.moveBy(fragment.paginationOffset);
-            result.unite(fragmentRect);
-        }
-    }
+    for (auto* columnSet : m_multiColumnSetList)
+        result.unite(columnSet->fragmentsBoundingBox(layerBoundingBox));
 
     return result;
 }