refactor: ginify powerMonitor (#22751)

shell/common/gin_helper/pinnable.h

@@ -0,0 +1,34 @@
+// Copyright (c) 2020 Slack Technologies, Inc.
+// Use of this source code is governed by the MIT license that can be
+// found in the LICENSE file.
+
+#ifndef SHELL_COMMON_GIN_HELPER_PINNABLE_H_
+#define SHELL_COMMON_GIN_HELPER_PINNABLE_H_
+
+#include "v8/include/v8.h"
+
+namespace gin_helper {
+
+template <typename T>
+class Pinnable {
+ protected:
+  // Prevent the object from being garbage collected until Unpin() is called.
+  void Pin(v8::Isolate* isolate) {
+    v8::Locker locker(isolate);
+    v8::HandleScope scope(isolate);
+    v8::Local<v8::Value> wrapper;
+    if (static_cast<T*>(this)->GetWrapper(isolate).ToLocal(&wrapper)) {
+      pinned_.Reset(isolate, wrapper);
+    }
+  }
+
+  // Allow the object to be garbage collected.
+  void Unpin() { pinned_.Reset(); }
+
+ private:
+  v8::Global<v8::Value> pinned_;
+};
+
+}  // namespace gin_helper
+
+#endif  // SHELL_COMMON_GIN_HELPER_PINNABLE_H_