Remove 64-bit unclean line from heap size estimation

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 1063 matching lines @@
   bool ReserveSpace(Reservation* reservations);
 
   //
   // Support for the API.
   //
 
   void CreateApiObjects();
 
   inline intptr_t PromotedTotalSize() {
     int64_t total = PromotedSpaceSizeOfObjects() + PromotedExternalMemorySize();
-    if (total > kMaxInt) return static_cast<intptr_t>(kMaxInt);

[Hannes Payer (out of office), 2015/05/15 15:08:19]

Unfortunatly, an overflow is possible here. jkummerow, what caused the
regression?

     if (total < 0) return 0;
     return static_cast<intptr_t>(total);
   }
 
   inline intptr_t OldGenerationSpaceAvailable() {
     return old_generation_allocation_limit_ - PromotedTotalSize();
   }
 
   inline intptr_t OldGenerationCapacityAvailable() {
     return max_old_generation_size_ - PromotedTotalSize();
@@ skipping 1542 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_