Make object groups and implicit references a bit more lightweight.

test/cctest/test-mark-compact.cc

Index: test/cctest/test-mark-compact.cc
diff --git a/test/cctest/test-mark-compact.cc b/test/cctest/test-mark-compact.cc
index 6d1b5ce632529c7e0bf18037262cb35e0943633d..a924c17f36f2d0a6e60a0b8ea9940ab30a8e9db5 100644
--- a/test/cctest/test-mark-compact.cc
+++ b/test/cctest/test-mark-compact.cc
@@ -308,9 +308,9 @@ TEST(ObjectGroups) {
   Handle<Object> g1s1 =
       global_handles->Create(HEAP->AllocateFixedArray(1)->ToObjectChecked());
   Handle<Object> g1s2 =
-    global_handles->Create(HEAP->AllocateFixedArray(1)->ToObjectChecked());
+      global_handles->Create(HEAP->AllocateFixedArray(1)->ToObjectChecked());
   Handle<Object> g1c1 =
-    global_handles->Create(HEAP->AllocateFixedArray(1)->ToObjectChecked());
+      global_handles->Create(HEAP->AllocateFixedArray(1)->ToObjectChecked());
   global_handles->MakeWeak(g1s1.location(),
                            reinterpret_cast<void*>(1234),
                            &WeakPointerCallback);
@@ -349,11 +349,11 @@ TEST(ObjectGroups) {
     Object** g2_objects[] = { g2s1.location(), g2s2.location() };
     Object** g2_children[] = { g2c1.location() };
     global_handles->AddObjectGroup(g1_objects, 2, NULL);
-    global_handles->AddImplicitReferences(HeapObject::cast(*g1s1),
-                                          g1_children, 1);
+    global_handles->AddImplicitReferences(
+        Handle<HeapObject>::cast(g1s1).location(), g1_children, 1);
     global_handles->AddObjectGroup(g2_objects, 2, NULL);
-    global_handles->AddImplicitReferences(HeapObject::cast(*g2s2),
-                                          g2_children, 1);
+    global_handles->AddImplicitReferences(
+        Handle<HeapObject>::cast(g2s2).location(), g2_children, 1);
   }
   // Do a full GC
   HEAP->CollectGarbage(OLD_POINTER_SPACE);
@@ -377,11 +377,11 @@ TEST(ObjectGroups) {
     Object** g2_objects[] = { g2s1.location(), g2s2.location() };
     Object** g2_children[] = { g2c1.location() };
     global_handles->AddObjectGroup(g1_objects, 2, NULL);
-    global_handles->AddImplicitReferences(HeapObject::cast(*g1s1),
-                                         g1_children, 1);
+    global_handles->AddImplicitReferences(
+        Handle<HeapObject>::cast(g1s1).location(), g1_children, 1);
     global_handles->AddObjectGroup(g2_objects, 2, NULL);
-    global_handles->AddImplicitReferences(HeapObject::cast(*g2s2),
-                                         g2_children, 1);
+    global_handles->AddImplicitReferences(
+        Handle<HeapObject>::cast(g2s2).location(), g2_children, 1);
   }
 
   HEAP->CollectGarbage(OLD_POINTER_SPACE);