Oilpan: Adjust FreeList::m_biggestFreeListIndex in ThreadHeap<Header>::merge().

If the split-off heap had free-list entries lager than the biggest one in the
main heap, they were not recycled.

BUG=420515

Review URL: https://codereview.chromium.org/712293002

git-svn-id: svn://svn.chromium.org/blink/trunk@185107 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/platform/heap/Heap.cpp

@@ -2767,6 +2767,8 @@ void ThreadHeap<Header>::merge(PassOwnPtr<BaseHeap> splitOffBase)
                 m_freeList.m_lastFreeListEntries[i] = splitOff->m_freeList.m_lastFreeListEntries[i];
             }
         }
+        if (m_freeList.m_biggestFreeListIndex < splitOff->m_freeList.m_biggestFreeListIndex)
+            m_freeList.m_biggestFreeListIndex = splitOff->m_freeList.m_biggestFreeListIndex;
     }
 }