[heap] Remove some more dead code in MC

src/heap/mark-compact.cc

 // 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.
 
 #include "src/heap/mark-compact.h"
 
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
 #include "src/base/sys-info.h"
 #include "src/code-stubs.h"
@@ skipping 4106 matching lines @@
                                   GCTracer::Scope::MC_SWEEP_MAP);
       StartSweepSpace(heap()->map_space());
     }
     sweeper().StartSweeping();
   }
 
   // Deallocate unmarked large objects.
   heap_->lo_space()->FreeUnmarkedObjects();
 }
 
-Isolate* MarkCompactCollector::isolate() const { return heap_->isolate(); }
-
-
 void MarkCompactCollector::Initialize() {
   MarkCompactMarkingVisitor::Initialize();
   IncrementalMarking::Initialize();
 }
 
 void MarkCompactCollector::RecordCodeEntrySlot(HeapObject* host, Address slot,
                                                Code* target) {
   Page* target_page = Page::FromAddress(reinterpret_cast<Address>(target));
   Page* source_page = Page::FromAddress(reinterpret_cast<Address>(host));
   if (target_page->IsEvacuationCandidate() &&
@@ skipping 17 matching lines @@
       // The target is always in old space, we don't have to record the slot in
       // the old-to-new remembered set.
       DCHECK(!heap()->InNewSpace(target));
       RecordRelocSlot(host, &rinfo, target);
     }
   }
 }
 
 }  // namespace internal
 }  // namespace v8