refactor: Clean up the implementation of the registerStreamProtocol (#11357)

* Use weak pointer to avoid race condition

* Use DeleteSoon to delete pointer across threads

* Simplify EventSubscriber

* No need to manually mange V8 convertions

* Fix cpplint warning

We should update cpplint for this, but let's do it in other PR.

* Move UI thread operations to EventSubscriber

* Less and more assertions

Some methods are now private so no more need to assert threads.

* Fix cpplint warnings

* No longer needs the EventEmitted

* EventSubscriber => StreamSubscriber

* Reduce the copies when passing data

* Fix cpplint warnings

atom/browser/api/stream_subscriber.h

@@ -0,0 +1,58 @@
+// Copyright (c) 2017 GitHub, Inc.
+// Use of this source code is governed by the MIT license that can be
+// found in the LICENSE file.
+
+#ifndef ATOM_BROWSER_API_STREAM_SUBSCRIBER_H_
+#define ATOM_BROWSER_API_STREAM_SUBSCRIBER_H_
+
+#include <map>
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "base/callback.h"
+#include "base/memory/weak_ptr.h"
+#include "content/public/browser/browser_thread.h"
+#include "v8/include/v8.h"
+
+namespace atom {
+class URLRequestStreamJob;
+}
+
+namespace mate {
+
+class Arguments;
+
+class StreamSubscriber {
+ public:
+  StreamSubscriber(v8::Isolate* isolate,
+                  v8::Local<v8::Object> emitter,
+                  base::WeakPtr<atom::URLRequestStreamJob> url_job);
+  ~StreamSubscriber();
+
+ private:
+  using JSHandlersMap = std::map<std::string, v8::Global<v8::Value>>;
+  using EventCallback = base::Callback<void(mate::Arguments* args)>;
+
+  void On(const std::string& event, EventCallback&& callback);  // NOLINT
+  void Off(const std::string& event);
+
+  void OnData(mate::Arguments* args);
+  void OnEnd(mate::Arguments* args);
+  void OnError(mate::Arguments* args);
+
+  void RemoveAllListeners();
+  void RemoveListener(JSHandlersMap::iterator it);
+
+  v8::Isolate* isolate_;
+  v8::Global<v8::Object> emitter_;
+  base::WeakPtr<atom::URLRequestStreamJob> url_job_;
+
+  JSHandlersMap js_handlers_;
+
+  base::WeakPtrFactory<StreamSubscriber> weak_factory_;
+};
+
+}  // namespace mate
+
+#endif  // ATOM_BROWSER_API_STREAM_SUBSCRIBER_H_