7048342: CMS: eob == _limit || fc->isFree() failed: Only a free chunk should...

7048342: CMS: eob == _limit || fc->isFree() failed: Only a free chunk should allow us to cross over the limit
Summary: The freeness bit was being cleared in debug code when it shouldn't have been. Also removed unused FreeChunk methods linkAfterNonNull and clearPrev.
Reviewed-by: brutisso

src/share/vm/gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.cpp

@@ -1833,8 +1833,6 @@ CompactibleFreeListSpace::removeChunkFromIndexedFreeList(FreeChunk* fc) {
     }
   )
   _indexedFreeList[size].removeChunk(fc);
-  debug_only(fc->clearNext());
-  debug_only(fc->clearPrev());
   NOT_PRODUCT(
     if (FLSVerifyIndexTable) {
       verifyIndexedFreeList(size);

src/share/vm/gc_implementation/concurrentMarkSweep/freeChunk.hpp

@@ -114,17 +114,11 @@ class FreeChunk VALUE_OBJ_CLASS_SPEC {
     linkNext(ptr);
     if (ptr != NULL) ptr->linkPrev(this);
   }
-  void linkAfterNonNull(FreeChunk* ptr) {
-    assert(ptr != NULL, "precondition violation");
-    linkNext(ptr);
-    ptr->linkPrev(this);
-  }
   void linkNext(FreeChunk* ptr) { _next = ptr; }
   void linkPrev(FreeChunk* ptr) {
     LP64_ONLY(if (UseCompressedOops) _prev = ptr; else)
     _prev = (FreeChunk*)((intptr_t)ptr | 0x1);
   }
-  void clearPrev()              { _prev = NULL; }
   void clearNext()              { _next = NULL; }
   void markNotFree() {
     // Set _prev (klass) to null before (if) clearing the mark word below