[heap] Remove obsolete DisallowAllocationFailure scope.

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 <map>
 
@@ skipping 2408 matching lines @@
   int* end_marker;                         // 22
 };
 
 
 class AlwaysAllocateScope {
  public:
   explicit inline AlwaysAllocateScope(Isolate* isolate);
   inline ~AlwaysAllocateScope();
 
  private:
-  // Implicitly disable artificial allocation failures.
   Heap* heap_;
-  DisallowAllocationFailure daf_;
 };
 
 
 class GCCallbacksScope {
  public:
   explicit inline GCCallbacksScope(Heap* heap);
   inline ~GCCallbacksScope();
 
   inline bool CheckReenter();
 
@@ skipping 304 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_