Remove conservative sweeping.

src/heap/heap.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HEAP_HEAP_H_
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
 
 #include "src/allocation.h"
@@ skipping 695 matching lines @@
   inline Object* ToBoolean(bool condition);
 
   // Performs garbage collection operation.
   // Returns whether there is a chance that another major GC could
   // collect more garbage.
   inline bool CollectGarbage(
       AllocationSpace space, const char* gc_reason = NULL,
       const GCCallbackFlags gc_callback_flags = kNoGCCallbackFlags);
 
   static const int kNoGCFlags = 0;
-  static const int kSweepPreciselyMask = 1;
-  static const int kReduceMemoryFootprintMask = 2;
-  static const int kAbortIncrementalMarkingMask = 4;
+  static const int kReduceMemoryFootprintMask = 1;
+  static const int kAbortIncrementalMarkingMask = 2;
 
-  // Making the heap iterable requires us to sweep precisely and abort any
-  // incremental marking as well.
-  static const int kMakeHeapIterableMask =
-      kSweepPreciselyMask | kAbortIncrementalMarkingMask;
+  // Making the heap iterable requires us to abort incremental marking.
+  static const int kMakeHeapIterableMask = kAbortIncrementalMarkingMask;
 
   // Performs a full garbage collection.  If (flags & kMakeHeapIterableMask) is
   // non-zero, then the slower precise sweeper is used, which leaves the heap
   // in a state where we can iterate over the heap visiting all objects.
   void CollectAllGarbage(
       int flags, const char* gc_reason = NULL,
       const GCCallbackFlags gc_callback_flags = kNoGCCallbackFlags);
 
   // Last hope GC, should try to squeeze as much as possible.
   void CollectAllAvailableGarbage(const char* gc_reason = NULL);
@@ skipping 1786 matching lines @@
   DisallowHeapAllocation no_allocation;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG
 }
 }  // namespace v8::internal
 
 #endif  // V8_HEAP_HEAP_H_