Wait for cancelable task after tearing down the heap.

BUG=

Review URL: https://codereview.chromium.org/1462573002

Cr-Commit-Position: refs/heads/master@{#32093}

src/isolate.cc

@@ -1921,11 +1921,11 @@ void Isolate::Deinit() {
   delete basic_block_profiler_;
   basic_block_profiler_ = NULL;
 
-  cancelable_task_manager()->CancelAndWait();
-
   heap_.TearDown();
   logger_->TearDown();
 
+  cancelable_task_manager()->CancelAndWait();
+
   delete heap_profiler_;
   heap_profiler_ = NULL;
   delete cpu_profiler_;