Oilpan: support eager finalization/sweeping.

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 699866a4516830374b32646ac8351c86a8c97e33..c75b6e0a3c0e9484e21dfa377c484200faa58376 100644
--- a/Source/platform/heap/ThreadState.cpp
+++ b/Source/platform/heap/ThreadState.cpp
@@ -912,6 +912,7 @@ void ThreadState::preSweep()
     } else {
         // The default behavior is lazy sweeping.
         setGCState(Sweeping);
+        eagerSweep();
         scheduleIdleLazySweep();
     }
 #else
@@ -926,6 +927,29 @@ void ThreadState::preSweep()
 #endif
 }
 
+void ThreadState::eagerSweep()
+{
+    // Some objects need to be finalized promptly and cannot be handled
+    // by lazy sweeping. Keep those in a designated heap and sweep it
+    // eagerly.
+    ASSERT(isSweepingInProgress());
+
+    // Mirroring the completeSweep() condition; see its comment.
+    if (sweepForbidden())
+        return;
+
+    ThreadState::SweepForbiddenScope scope(this);
+    {
+        if (isMainThread())
+            ScriptForbiddenScope::enter();
+
+        m_heaps[EagerSweepHeapIndex]->completeSweep();
+
+        if (isMainThread())
+            ScriptForbiddenScope::exit();
+    }
+}
+
 void ThreadState::completeSweep()
 {
     // If we are not in a sweeping phase, there is nothing to do here.