Rename findSetLayoutObjects() to mapDescendantToColumnSet()

Source/core/layout/LayoutMultiColumnFlowThread.h

Index: Source/core/layout/LayoutMultiColumnFlowThread.h
diff --git a/Source/core/layout/LayoutMultiColumnFlowThread.h b/Source/core/layout/LayoutMultiColumnFlowThread.h
index baff32b39619ebe1514abb147f88aaa2bcd2f489..6ef247e30653e95addbe571d9634ce513466a879 100644
--- a/Source/core/layout/LayoutMultiColumnFlowThread.h
+++ b/Source/core/layout/LayoutMultiColumnFlowThread.h
@@ -142,8 +142,8 @@ public:
         return lastSiblingBox != this ? lastSiblingBox : 0;
     }
 
-    // Find the first set inside which the specified layoutObject would be rendered.
-    LayoutMultiColumnSet* findSetLayoutObjects(LayoutObject*) const;
+    // Find the first set inside which the specified layoutObject (which is a flowthread descendant) would be rendered.
+    LayoutMultiColumnSet* mapDescendantToColumnSet(LayoutObject*) const;
 
     // Return the spanner placeholder that belongs to the spanner in the containing block chain, if
     // any. This includes the layoutObject for the element that actually establishes the spanner too.