Revert of Oilpan: Implement a GC to take a heap snapshot

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 d5c4c4cb639919fe60c5f051a48eff3fdd593bf1..3b2c8d649be43b4dc04a4e88083f4b4c0947efe3 100644
--- a/Source/platform/heap/ThreadState.h
+++ b/Source/platform/heap/ThreadState.h
@@ -178,14 +178,8 @@
     };
 
     enum GCType {
-        // Run a marking task and a sweeping task in Heap::collectGarbage().
-        GCWithSweep,
-        // Run only a marking task in Heap::collectGarbage(). A sweeping task
-        // is split into chunks and scheduled lazily.
-        GCWithoutSweep,
-        // Run a marking task just to take a heap snapshot. A sweeping task
-        // doesn't run and the marks are just dropped.
-        TakeSnapshot,
+        GCWithSweep, // Sweeping is completed in Heap::collectGarbage().
+        GCWithoutSweep, // Lazy sweeping is scheduled.
     };
 
     // See setGCState() for possible state transitions.
@@ -340,8 +334,8 @@
     //   In this case, the next GC just cancels the remaining lazy sweeping.
     //   Specifically, preGC() of the next GC calls makeConsistentForSweeping()
     //   and it marks all not-yet-swept objets as dead.
-    void makeConsistentForSweeping(GCType);
-    void preGC(GCType);
+    void makeConsistentForSweeping();
+    void preGC();
     void postGC(GCType);
     void preSweep();
     void completeSweep();
@@ -656,7 +650,6 @@
     void unregisterPreFinalizerInternal(void*);
     void invokePreFinalizers(Visitor&);
 
-    void takeSnapshot();
 #if ENABLE(GC_PROFILING)
     void snapshotFreeList();
 #endif