Comment out %RunMicrotasks assert that triggers in mjsunit tests

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index a07451a9bed2ffc3f375b5b38b533626a9b9529f..99af8fad36f56f18f5d28516544a2680496b1045 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -2264,7 +2264,12 @@ void Isolate::EnqueueMicrotask(Handle<JSFunction> microtask) {
 
 
 void Isolate::RunMicrotasks() {
-  ASSERT(handle_scope_implementer()->CallDepthIsZero());
+  // TODO(adamk): This ASSERT triggers in mjsunit tests which
+  // call the %RunMicrotasks runtime function. But it should
+  // never happen outside of tests, so it would be nice to
+  // uncomment it.
+  //
+  // ASSERT(handle_scope_implementer()->CallDepthIsZero());
 
   // Increase call depth to prevent recursive callbacks.
   handle_scope_implementer()->IncrementCallDepth();