[heap] Add unit tests for Worklist::FlushToGlobal.

BUG=chromium:694255

Change-Id: I3e9c5e6b47b4dd0fbd2524b3329dbef14d4ad4e7
Reviewed-on: https://chromium-review.googlesource.com/550158Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46267}

test/unittests/heap/worklist-unittest.cc

@@ -191,6 +191,32 @@ TEST(Worklist, GlobalUpdate) {
   }
 }
 
+TEST(Worklist, FlushToGlobalPushSegment) {
+  Worklist worklist;
+  WorklistView worklist_view0(&worklist, 0);
+  WorklistView worklist_view1(&worklist, 1);
+  HeapObject* object = nullptr;
+  HeapObject* objectA = nullptr;
+  objectA = reinterpret_cast<HeapObject*>(&objectA);
+  EXPECT_TRUE(worklist_view0.Push(objectA));
+  worklist.FlushToGlobal(0);
+  EXPECT_TRUE(worklist_view1.Pop(&object));
+}
+
+TEST(Worklist, FlushToGlobalPopSegment) {
+  Worklist worklist;
+  WorklistView worklist_view0(&worklist, 0);
+  WorklistView worklist_view1(&worklist, 1);
+  HeapObject* object = nullptr;
+  HeapObject* objectA = nullptr;
+  objectA = reinterpret_cast<HeapObject*>(&objectA);
+  EXPECT_TRUE(worklist_view0.Push(objectA));
+  EXPECT_TRUE(worklist_view0.Push(objectA));
+  EXPECT_TRUE(worklist_view0.Pop(&object));
+  worklist.FlushToGlobal(0);
+  EXPECT_TRUE(worklist_view1.Pop(&object));
+}
+
 TEST(Worklist, Clear) {
   Worklist worklist;
   WorklistView worklist_view(&worklist, 0);