Fix cctest/test-spaces/CompactionSpace

kExpectedPages should be ceil(kNumObjects / kNumObjectsPerPage)

R=mlippautz@chromium.org, hpayer@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1418143004

Cr-Commit-Position: refs/heads/master@{#31605}

test/cctest/test-spaces.cc

@@ -429,8 +429,10 @@ TEST(CompactionSpace) {
   // Cannot loop until "Available()" since we initially have 0 bytes available
   // and would thus neither grow, nor be able to allocate an object.
   const int kNumObjects = 100;
-  const int kExpectedPages = (kNumObjects / (compaction_space->AreaSize() /
-                                             Page::kMaxRegularHeapObjectSize));
+  const int kNumObjectsPerPage =
+      compaction_space->AreaSize() / Page::kMaxRegularHeapObjectSize;
+  const int kExpectedPages =
+      (kNumObjects + kNumObjectsPerPage - 1) / kNumObjectsPerPage;
   for (int i = 0; i < kNumObjects; i++) {
     compaction_space->AllocateRawUnaligned(Page::kMaxRegularHeapObjectSize)
         .ToObjectChecked();