[heap] Fix -Wsign-compare warnings

src/heap/spaces.h

 // Copyright 2011 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_SPACES_H_
 #define V8_HEAP_SPACES_H_
 
 #include <list>
 #include <memory>
 #include <unordered_set>
@@ skipping 1625 matching lines @@
 // 256-2047 words (medium): Used for allocating free space between 32-255 words
 //   in size.
 // 1048-16383 words (large): Used for allocating free space between 256-2047
 //   words in size.
 // At least 16384 words (huge): This list is for objects of 2048 words or
 //   larger. Empty pages are also added to this list.
 class FreeList {
  public:
   // This method returns how much memory can be allocated after freeing
   // maximum_freed memory.
-  static inline int GuaranteedAllocatable(int maximum_freed) {
+  static inline size_t GuaranteedAllocatable(size_t maximum_freed) {
     if (maximum_freed <= kTiniestListMax) {
       // Since we are not iterating over all list entries, we cannot guarantee
       // that we can find the maximum freed block in that free list.
       return 0;
     } else if (maximum_freed <= kTinyListMax) {
       return kTinyAllocationMax;
     } else if (maximum_freed <= kSmallListMax) {
       return kSmallAllocationMax;
     } else if (maximum_freed <= kMediumListMax) {
       return kMediumAllocationMax;
@@ skipping 21 matching lines @@
   // Clear the free list.
   void Reset();
 
   void ResetStats() {
     wasted_bytes_.SetValue(0);
     ForAllFreeListCategories(
         [](FreeListCategory* category) { category->ResetStats(); });
   }
 
   // Return the number of bytes available on the free list.
-  intptr_t Available() {
-    intptr_t available = 0;
+  size_t Available() {
+    size_t available = 0;
     ForAllFreeListCategories([&available](FreeListCategory* category) {
       available += category->available();
     });
     return available;
   }
 
   bool IsEmpty() {
     bool empty = true;
     ForAllFreeListCategories([&empty](FreeListCategory* category) {
       if (!category->is_empty()) empty = false;
@@ skipping 1200 matching lines @@
   PageIterator old_iterator_;
   PageIterator code_iterator_;
   PageIterator map_iterator_;
   LargePageIterator lo_iterator_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_SPACES_H_