Clean up comment.

src/mark-compact.h

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 157 matching lines @@
   // is why we can use this field temporarily for back pointers.
   static void CreateBackPointers();
 
   // Mark a Map and its DescriptorArray together, skipping transitions.
   static void MarkMapContents(Map* map);
   static void MarkDescriptorArray(DescriptorArray* descriptors);
 
   // Mark the heap roots and all objects reachable from them.
   static void MarkRoots(RootMarkingVisitor* visitor);
 
-  // Mark the symbol table specially.  References to symbols are weak.
+  // Mark the symbol table specially.  References to symbols from the
+  // symbol table are weak.
   static void MarkSymbolTable();
 
   // Mark objects in object groups that have at least one object in the
   // group marked.
   static void MarkObjectGroups();
 
   // Mark all objects in an object group with at least one marked
   // object, then all objects reachable from marked objects in object
   // groups, and repeat.
   static void ProcessObjectGroups(MarkingVisitor* visitor);
@@ skipping 216 matching lines @@
 
   friend class UnmarkObjectVisitor;
   static void UnmarkObject(HeapObject* obj);
 #endif
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_MARK_COMPACT_H_