PPC: [test] fix heap/Regress589413

We need to reserve two pages for young objects and objects on
the evacuation candidate page.

Change-Id: I0c4e8f85971676c0b50dfd947678a33dd1b56084
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2224364Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68110}

test/cctest/heap/test-heap.cc

@@ -5475,8 +5475,10 @@ HEAP_TEST(Regress589413) {
       // Add the array in root set.
       handle(array, isolate);
     }
-    // Expand and fill one complete page with fixed arrays.
     heap->set_force_oom(false);
+    size_t initial_pages = pages.size();
+    // Expand and fill two pages with fixed array to ensure enough space both
+    // the young objects and the evacuation candidate pages.
     while (
         AllocateFixedArrayForTest(heap, N, AllocationType::kOld).To(&array)) {
       arrays.push_back(array);
@@ -5484,7 +5486,9 @@ HEAP_TEST(Regress589413) {
       // Add the array in root set.
       handle(array, isolate);
       // Do not expand anymore.
-      heap->set_force_oom(true);
+      if (pages.size() - initial_pages == 2) {
+        heap->set_force_oom(true);
+      }
     }
     // Expand and mark the new page as evacuation candidate.
     heap->set_force_oom(false);