[heap] Reduce size of large object in StressConcurrentAllocatorTask

This ensures that large object has exactly the size of a regular page.
Avoids wasting memory due to alignment.

Bug: v8:10315
Change-Id: Ife8051313f1ea8c1fc0ba0afcc4e5db11f27adca
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2335191Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69225}

src/heap/concurrent-allocator.cc

@@ -10,6 +10,7 @@
 #include "src/heap/concurrent-allocator-inl.h"
 #include "src/heap/local-heap-inl.h"
 #include "src/heap/marking.h"
+#include "src/heap/memory-chunk.h"
 
 namespace v8 {
 namespace internal {
@@ -21,7 +22,9 @@ void StressConcurrentAllocatorTask::RunInternal() {
   const int kNumIterations = 2000;
   const int kSmallObjectSize = 10 * kTaggedSize;
   const int kMediumObjectSize = 8 * KB;
-  const int kLargeObjectSize = kMaxRegularHeapObjectSize * 2;
+  const int kLargeObjectSize =
+      static_cast<int>(MemoryChunk::kPageSize -
+                       MemoryChunkLayout::ObjectStartOffsetInDataPage());
 
   for (int i = 0; i < kNumIterations; i++) {
     Address address = local_heap.AllocateRawOrFail(