Oilpan: move "forced GC" handling back to gcEpilogue().

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 760689818b8d36969e9a433e36a72c201fa615cf..c45605a914098356bdf20fa59cae74e1e1206eea 100644
--- a/Source/platform/heap/ThreadState.cpp
+++ b/Source/platform/heap/ThreadState.cpp
@@ -817,7 +817,7 @@ ThreadState::GCState ThreadState::gcState() const
     return m_gcState;
 }
 
-void ThreadState::didV8MajorGC(bool forceGC)
+void ThreadState::didV8MajorGC()
 {
     checkThread();
     if (isMainThread()) {
@@ -826,24 +826,6 @@ void ThreadState::didV8MajorGC(bool forceGC)
         // references to their DOM objects.
         Heap::setEstimatedLiveObjectSize(Heap::estimatedLiveObjectSize() / 2);
 
-        if (forceGC) {
-            // This single GC is not enough for two reasons:
-            //   (1) The GC is not precise because the GC scans on-stack pointers conservatively.
-            //   (2) One GC is not enough to break a chain of persistent handles. It's possible that
-            //       some heap allocated objects own objects that contain persistent handles
-            //       pointing to other heap allocated objects. To break the chain, we need multiple GCs.
-            //
-            // Regarding (1), we force a precise GC at the end of the current event loop. So if you want
-            // to collect all garbage, you need to wait until the next event loop.
-            // Regarding (2), it would be OK in practice to trigger only one GC per gcEpilogue, because
-            // GCController.collectAll() forces 7 V8's GC.
-            Heap::collectGarbage(ThreadState::HeapPointersOnStack, ThreadState::GCWithSweep, Heap::ForcedGC);
-
-            // Forces a precise GC at the end of the current event loop.
-            ThreadState::current()->setGCState(ThreadState::FullGCScheduled);
-            return;
-        }
-
         // If under memory pressure, complete sweeping before initiating
         // the urgent conservative GC.
         if (shouldForceMemoryPressureGC())