Oilpan: support eager finalization/sweeping.

Source/platform/heap/ThreadState.h

Index: Source/platform/heap/ThreadState.h
diff --git a/Source/platform/heap/ThreadState.h b/Source/platform/heap/ThreadState.h
index 459b8acd854aa0178a933f85b33cea1ea8f0e366..6c54dfed56576c33f5dcf76cf1241383f646699a 100644
--- a/Source/platform/heap/ThreadState.h
+++ b/Source/platform/heap/ThreadState.h
@@ -141,6 +141,7 @@ enum HeapIndices {
     NormalPage2HeapIndex,
     NormalPage3HeapIndex,
     NormalPage4HeapIndex,
+    EagerSweepHeapIndex,
     Vector1HeapIndex,
     Vector2HeapIndex,
     Vector3HeapIndex,
@@ -633,6 +634,8 @@ private:
     bool shouldForceConservativeGC();
     void runScheduledGC(StackState);
 
+    void eagerSweep();
+
     // When ThreadState is detaching from non-main thread its
     // heap is expected to be empty (because it is going away).
     // Perform registered cleanup tasks and garbage collection