[cctests] Check for stray Isolates in DEBUG builds

Bug: 
Change-Id: Id3373279f2d985f7899cf893c1f63692b97166b7
Reviewed-on: https://chromium-review.googlesource.com/704655
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48456}

src/isolate.cc

@@ -2320,6 +2320,10 @@ class VerboseAccountingAllocator : public AccountingAllocator {
   size_t allocation_sample_bytes_, pool_sample_bytes_;
 };
 
+#ifdef DEBUG
+base::AtomicNumber<size_t> Isolate::non_disposed_isolates_;
+#endif  // DEBUG
+
 Isolate::Isolate(bool enable_serializer)
     : embedder_data_(),
       entry_stack_(NULL),
@@ -2403,7 +2407,9 @@ Isolate::Isolate(bool enable_serializer)
 #ifdef DEBUG
   // heap_histograms_ initializes itself.
   memset(&js_spill_information_, 0, sizeof(js_spill_information_));
-#endif
+
+  non_disposed_isolates_.Increment(1);
+#endif  // DEBUG
 
   handle_scope_data_.Initialize();
 
@@ -2444,6 +2450,10 @@ void Isolate::TearDown() {
     thread_data_table_->RemoveAllThreads(this);
   }
 
+#ifdef DEBUG
+  non_disposed_isolates_.Decrement(1);
+#endif  // DEBUG
+
   delete this;
 
   // Restore the previous current isolate.

src/isolate.h

@@ -980,6 +980,10 @@ class Isolate {
   HeapProfiler* heap_profiler() const { return heap_profiler_; }
 
 #ifdef DEBUG
+  static size_t non_disposed_isolates() {
+    return non_disposed_isolates_.Value();
+  }
+
   HistogramInfo* heap_histograms() { return heap_histograms_; }
 
   JSObject::SpillInformation* js_spill_information() {
@@ -1523,6 +1527,8 @@ class Isolate {
   double time_millis_at_init_;
 
 #ifdef DEBUG
+  static base::AtomicNumber<size_t> non_disposed_isolates_;
+
   // A static array of histogram info for each type.
   HistogramInfo heap_histograms_[LAST_TYPE + 1];
   JSObject::SpillInformation js_spill_information_;

test/cctest/cctest.cc

@@ -95,7 +95,17 @@ void CcTest::Run() {
     }
     isolate_->Enter();
   }
+#ifdef DEBUG
+  const size_t active_isolates = i::Isolate::non_disposed_isolates();
+#endif  // DEBUG
   callback_();
+#ifdef DEBUG
+  // This DCHECK ensures that all Isolates are properly disposed after finishing
+  // the test. Stray Isolates lead to stray tasks in the platform which can
+  // interact weirdly when swapping in new platforms (for testing) or during
+  // shutdown.
+  DCHECK_EQ(active_isolates, i::Isolate::non_disposed_isolates());
+#endif  // DEBUG
   if (initialize_) {
     if (v8::Locker::IsActive()) {
       v8::Locker locker(isolate_);