Oilpan: Add more trace events to platform/heap/

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 b90d493bf63ac4bf71a69da752add1a52661eee5..58efa8d7d4b66fc55fb4cff1d21df3164468ce0d 100644
--- a/Source/platform/heap/ThreadState.cpp
+++ b/Source/platform/heap/ThreadState.cpp
@@ -1042,7 +1042,11 @@ public:
         m_threadState->unregisterSweepingTask();
     }
 
-    virtual void run() { m_heap->sweep(m_stats); }
+    virtual void run()
+    {
+        TRACE_EVENT0("blink_gc", "ThreadState::sweepNonFinalizedHeaps");
+        m_heap->sweep(m_stats);
+    }
 
 private:
     ThreadState* m_threadState;