Run JS micro tasks in the appropriate context.

src/isolate.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <stdlib.h>
 
 #include "src/v8.h"
 
 #include "src/ast.h"
 #include "src/bootstrapper.h"
@@ skipping 2274 matching lines @@
     queue = FixedArray::CopySize(queue, num_tasks * 2);
     heap()->set_microtask_queue(*queue);
   }
   ASSERT(queue->get(num_tasks)->IsUndefined());
   queue->set(num_tasks, *microtask);
   set_pending_microtask_count(num_tasks + 1);
 }
 
 
 void Isolate::RunMicrotasks() {
-  // 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());
+  // In some mjsunit tests %RunMicrotasks is called explicitly, violating
+  // this assertion.  Therefore we also check for --allow-natives-syntax.
+  ASSERT(FLAG_allow_natives_syntax ||
+         handle_scope_implementer()->CallDepthIsZero());
 
   // Increase call depth to prevent recursive callbacks.
   v8::Isolate::SuppressMicrotaskExecutionScope suppress(
       reinterpret_cast<v8::Isolate*>(this));
 
   while (pending_microtask_count() > 0) {
     HandleScope scope(this);
     int num_tasks = pending_microtask_count();
     Handle<FixedArray> queue(heap()->microtask_queue(), this);
     ASSERT(num_tasks <= queue->length());
     set_pending_microtask_count(0);
     heap()->set_microtask_queue(heap()->empty_fixed_array());
 
     for (int i = 0; i < num_tasks; i++) {
       HandleScope scope(this);
       Handle<Object> microtask(queue->get(i), this);
       if (microtask->IsJSFunction()) {
         Handle<JSFunction> microtask_function =
             Handle<JSFunction>::cast(microtask);
+        SaveContext save(this);
+        set_context(microtask_function->context()->native_context());
         Handle<Object> exception;
         MaybeHandle<Object> result = Execution::TryCall(
             microtask_function, factory()->undefined_value(),
             0, NULL, &exception);
         // If execution is terminating, just bail out.
         if (result.is_null() &&
             !exception.is_null() &&
             *exception == heap()->termination_exception()) {
           // Clear out any remaining callbacks in the queue.
           heap()->set_microtask_queue(heap()->empty_fixed_array());
@@ skipping 19 matching lines @@
   // The simulator uses a separate JS stack.
   Address jssp_address = Simulator::current(isolate_)->get_sp();
   uintptr_t jssp = reinterpret_cast<uintptr_t>(jssp_address);
   if (jssp < stack_guard->real_jslimit()) return true;
 #endif  // USE_SIMULATOR
   return reinterpret_cast<uintptr_t>(this) < stack_guard->real_climit();
 }
 
 
 } }  // namespace v8::internal