Introduce a microtask suppression scope and move microtask methods to isolate

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index 72df9b4b2b131794190e025049fe65f4e8e51362..82ad5fc8bd9ce4b242a1f4818d804418b31a4e89 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -2252,4 +2252,17 @@ void Isolate::FireCallCompletedCallback() {
 }
 
 
+void Isolate::RunMicrotasks() {
+  if (!microtask_pending())
+    return;
+
+  ASSERT(handle_scope_implementer()->CallDepthIsZero());
+
+  // Increase call depth to prevent recursive callbacks.
+  handle_scope_implementer()->IncrementCallDepth();
+  Execution::RunMicrotasks(this);
+  handle_scope_implementer()->DecrementCallDepth();
+}
+
+
 } }  // namespace v8::internal