[gn] Enable stricter build flags

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 1628 matching lines @@
 
   StoreBuffer* store_buffer() { return store_buffer_; }
 
   void set_current_gc_flags(int flags) {
     current_gc_flags_ = flags;
     DCHECK(!ShouldFinalizeIncrementalMarking() ||
            !ShouldAbortIncrementalMarking());
   }
 
   inline bool ShouldReduceMemory() const {
-    return current_gc_flags_ & kReduceMemoryFootprintMask;
+    return (current_gc_flags_ & kReduceMemoryFootprintMask) != 0;
   }
 
   inline bool ShouldAbortIncrementalMarking() const {
-    return current_gc_flags_ & kAbortIncrementalMarkingMask;
+    return (current_gc_flags_ & kAbortIncrementalMarkingMask) != 0;
   }
 
   inline bool ShouldFinalizeIncrementalMarking() const {
-    return current_gc_flags_ & kFinalizeIncrementalMarkingMask;
+    return (current_gc_flags_ & kFinalizeIncrementalMarkingMask) != 0;
   }
 
   void PreprocessStackTraces();
 
   // Checks whether a global GC is necessary
   GarbageCollector SelectGarbageCollector(AllocationSpace space,
                                           const char** reason);
 
   // Make sure there is a filler value behind the top of the new space
   // so that the GC does not confuse some unintialized/stale memory
@@ skipping 946 matching lines @@
   friend class LargeObjectSpace;
   friend class NewSpace;
   friend class PagedSpace;
   DISALLOW_COPY_AND_ASSIGN(AllocationObserver);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_HEAP_H_