Fix more -Wsign-compare warnings in heap, mips, base, etc.

src/base/atomic-utils.h

 // Copyright 2015 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_ATOMIC_UTILS_H_
 #define V8_ATOMIC_UTILS_H_
 
 #include <limits.h>
 
 #include "src/base/atomicops.h"
@@ skipping 109 matching lines @@
   }
 
   V8_INLINE bool TrySetValue(T old_value, T new_value) {
     return base::Release_CompareAndSwap(
                &value_, cast_helper<T>::to_storage_type(old_value),
                cast_helper<T>::to_storage_type(new_value)) ==
            cast_helper<T>::to_storage_type(old_value);
   }
 
   V8_INLINE void SetBits(T bits, T mask) {
-    DCHECK_EQ(bits & ~mask, 0);
+    DCHECK_EQ(bits & ~mask, static_cast<T>(0));
     T old_value;
     T new_value;
     do {
       old_value = Value();
       new_value = (old_value & ~mask) | bits;
     } while (!TrySetValue(old_value, new_value));
   }
 
   V8_INLINE void SetBit(int bit) {
     SetBits(static_cast<T>(1) << bit, static_cast<T>(1) << bit);
@@ skipping 104 matching lines @@
     return static_cast<base::AtomicWord>(1) << element;
   }
 
   base::AtomicWord bits_;
 };
 
 }  // namespace base
 }  // namespace v8
 
 #endif  // #define V8_ATOMIC_UTILS_H_