[heap] Fix -Wsign-compare warnings

test/cctest/heap/heap-utils.cc

 // Copyright 2016 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 "test/cctest/heap/heap-utils.h"
 
 #include "src/factory.h"
 #include "src/heap/heap-inl.h"
 #include "src/heap/incremental-marking.h"
 #include "src/heap/mark-compact.h"
@@ skipping 20 matching lines @@
 }
 
 std::vector<Handle<FixedArray>> FillOldSpacePageWithFixedArrays(Heap* heap,
                                                                 int remainder) {
   std::vector<Handle<FixedArray>> handles;
   Isolate* isolate = heap->isolate();
   const int kArraySize = 128;
   const int kArrayLen = heap::FixedArrayLenFromSize(kArraySize);
   CHECK_EQ(Page::kAllocatableMemory % kArraySize, 0);
   Handle<FixedArray> array;
-  for (size_t allocated = 0;
-       allocated != (Page::kAllocatableMemory - remainder);
+  for (int allocated = 0; allocated != (Page::kAllocatableMemory - remainder);
        allocated += array->Size()) {
     if (allocated == (Page::kAllocatableMemory - kArraySize)) {
       array = isolate->factory()->NewFixedArray(
           heap::FixedArrayLenFromSize(kArraySize - remainder), TENURED);
       CHECK_EQ(kArraySize - remainder, array->Size());
     } else {
       array = isolate->factory()->NewFixedArray(kArrayLen, TENURED);
       CHECK_EQ(kArraySize, array->Size());
     }
     if (handles.empty()) {
@@ skipping 151 matching lines @@
     int remaining = static_cast<int>(limit - top);
     space->heap()->CreateFillerObjectAt(top, remaining,
                                         ClearRecordedSlots::kNo);
     space->SetTopAndLimit(nullptr, nullptr);
   }
 }
 
 }  // namespace heap
 }  // namespace internal
 }  // namespace v8