If a large object is truncated, also truncate the page.

runtime/vm/object_test.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 // TODO(zra): Remove when tests are ready to enable.
 #include "platform/globals.h"
 
 #include "vm/assembler.h"
 #include "vm/bigint_operations.h"
 #include "vm/class_finalizer.h"
@@ skipping 2043 matching lines @@
   left_over_array ^= obj.raw();
   EXPECT_EQ((6 * kWordSize), left_over_array.Length());
 
   // 4. Verify that GC can handle the filler object for a large array.
   array = GrowableObjectArray::New((1 * MB) >> kWordSizeLog2);
   EXPECT_EQ(0, array.Length());
   for (intptr_t i = 0; i < 1; i++) {
     value = Smi::New(i);
     array.Add(value);
   }
+  Heap* heap = Isolate::Current()->heap();
+  heap->CollectAllGarbage();
+  intptr_t capacity_before = heap->CapacityInWords(Heap::kOld);
   new_array = Array::MakeArray(array);
   EXPECT_EQ(1, new_array.Length());
-  Isolate::Current()->heap()->CollectAllGarbage();
+  heap->CollectAllGarbage();
+  intptr_t capacity_after = heap->CapacityInWords(Heap::kOld);
+  // Page should shrink.
+  EXPECT_LT(capacity_after, capacity_before);
   EXPECT_EQ(1, new_array.Length());
 }
 
 
 TEST_CASE(InternalTypedData) {
   uint8_t data[] = { 253, 254, 255, 0, 1, 2, 3, 4 };
   intptr_t data_length = ARRAY_SIZE(data);
 
   const TypedData& int8_array =
       TypedData::Handle(TypedData::New(kTypedDataInt8ArrayCid, data_length));
@@ skipping 2030 matching lines @@
   EXPECT_VALID(h_result);
   Integer& result = Integer::Handle();
   result ^= Api::UnwrapHandle(h_result);
   String& foo = String::Handle(String::New("foo"));
   Integer& expected = Integer::Handle();
   expected ^= foo.HashCode();
   EXPECT(result.IsIdenticalTo(expected));
 }
 
 }  // namespace dart