[oilpan]: Don't sweep while in safepoint.

Source/platform/heap/ThreadState.cpp

Index: Source/platform/heap/ThreadState.cpp
diff --git a/Source/platform/heap/ThreadState.cpp b/Source/platform/heap/ThreadState.cpp
index af776ba616d92b59d2873b8aa605cf9062bb9aea..b15a2362232652299e2b378a40b89fa7bff432c5 100644
--- a/Source/platform/heap/ThreadState.cpp
+++ b/Source/platform/heap/ThreadState.cpp
@@ -198,7 +198,6 @@ public:
             if (locker)
                 locker->reset();
             pushAllRegisters(this, state, parkAfterPushRegisters);
-            state->performPendingSweep();
         }
     }
 
@@ -758,6 +757,7 @@ void ThreadState::safePoint(StackState stackState)
     s_safePointBarrier->checkAndPark(this);
     m_atSafePoint = false;
     m_stackState = HeapPointersOnStack;
+    performPendingSweep();
 }
 
 #ifdef ADDRESS_SANITIZER