fix: let Node.js perform microtask checkpoint in the main process

shell/browser/electron_browser_main_parts.h

@@ -90,6 +90,7 @@ class ElectronBrowserMainParts : public content::BrowserMainParts {
 
   Browser* browser() { return browser_.get(); }
   BrowserProcessImpl* browser_process() { return fake_browser_process_.get(); }
+  NodeEnvironment* node_env() { return node_env_.get(); }
 
  protected:
   // content::BrowserMainParts:

shell/browser/javascript_environment.h

@@ -57,6 +57,8 @@ class NodeEnvironment {
   explicit NodeEnvironment(node::Environment* env);
   ~NodeEnvironment();
 
+  node::Environment* env() { return env_; }
+
  private:
   node::Environment* env_;
 

shell/browser/microtasks_runner.cc

@@ -4,6 +4,10 @@
 // found in the LICENSE file.
 
 #include "shell/browser/microtasks_runner.h"
+
+#include "shell/browser/electron_browser_main_parts.h"
+#include "shell/browser/javascript_environment.h"
+#include "shell/common/node_includes.h"
 #include "v8/include/v8.h"
 
 namespace electron {
@@ -15,7 +19,19 @@ void MicrotasksRunner::WillProcessTask(const base::PendingTask& pending_task,
 
 void MicrotasksRunner::DidProcessTask(const base::PendingTask& pending_task) {
   v8::Isolate::Scope scope(isolate_);
-  v8::MicrotasksScope::PerformCheckpoint(isolate_);
+  // In the browser process we follow Node.js microtask policy of kExplicit
+  // and let the MicrotaskRunner which is a task observer for chromium UI thread
+  // scheduler run the micotask checkpoint. This worked fine because Node.js
+  // also runs microtasks through its task queue, but after
+  // https://github.com/electron/electron/issues/20013 Node.js now performs its
+  // own microtask checkpoint and it may happen is some situations that there is
+  // contention for performing checkpoint between Node.js and chromium, ending
+  // up Node.js dealying its callbacks. To fix this, now we always lets Node.js
+  // handle the checkpoint in the browser process.
+  auto* node_env = electron::ElectronBrowserMainParts::Get()->node_env();
+  node::InternalCallbackScope microtask_scope(
+      node_env->env(), v8::Local<v8::Object>(), {0, 0},
+      node::InternalCallbackScope::kAllowEmptyResource);
 }
 
 }  // namespace electron