Fix vm/cc/Pages unittest breakage

runtime/vm/pages.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.
 
 #include "vm/pages.h"
 
 #include "platform/assert.h"
 #include "vm/compiler_stats.h"
 #include "vm/gc_marker.h"
 #include "vm/gc_sweeper.h"
@@ skipping 517 matching lines @@
 void PageSpace::AbandonBumpAllocation() {
   if (bump_top_ < bump_end_) {
     freelist_[HeapPage::kData].Free(bump_top_, bump_end_ - bump_top_);
     bump_top_ = 0;
     bump_end_ = 0;
   }
 }
 
 
 void PageSpace::UpdateMaxCapacityLocked() {
+  if (heap_ == NULL) {
+    // Some unit tests.
+    return;
+  }
   ASSERT(heap_ != NULL);
   ASSERT(heap_->isolate() != NULL);
   Isolate* isolate = heap_->isolate();
   isolate->GetHeapOldCapacityMaxMetric()->SetValue(
       static_cast<int64_t>(usage_.capacity_in_words) * kWordSize);
 }
 
 
 bool PageSpace::Contains(uword addr) const {
   for (ExclusivePageIterator it(this); !it.Done(); it.Advance()) {
@@ skipping 642 matching lines @@
     return 0;
   } else {
     ASSERT(total_time >= gc_time);
     int result = static_cast<int>((static_cast<double>(gc_time) /
                                    static_cast<double>(total_time)) * 100);
     return result;
   }
 }
 
 }  // namespace dart