WebWorkers: Add c++ API for working with MessageQueueThread

Summary:
public

Adds a fbjni API similar to JNativeRunnable so that you can post ##std::function<void()>## to MessageQueueThreads.

Reviewed By: lexs

Differential Revision: D2779094

fb-gh-sync-id: 8f873fc93fb6b817268e9422c0b6f85c3e453676

ReactAndroid/src/main/java/com/facebook/react/bridge/queue/MessageQueueThreadRegistry.java

@@ -29,6 +29,7 @@ public class MessageQueueThreadRegistry {
   /**
    * @return the MessageQueueThread that owns the current Thread.
    */
+  @DoNotStrip
   public static MessageQueueThread myMessageQueueThread() {
     return Assertions.assertNotNull(
         sMyMessageQueueThread.get(),

ReactAndroid/src/main/jni/react/jni/JMessageQueueThread.cpp

@@ -0,0 +1,32 @@
+// Copyright 2004-present Facebook. All Rights Reserved.
+
+#include "JMessageQueueThread.h"
+
+#include <fb/log.h>
+#include <folly/Memory.h>
+#include <jni/fbjni.h>
+
+#include "JNativeRunnable.h"
+
+namespace facebook {
+namespace react {
+
+JMessageQueueThread::JMessageQueueThread(alias_ref<MessageQueueThread::javaobject> jobj) :
+    m_jobj(make_global(jobj)) {
+}
+
+void JMessageQueueThread::runOnQueue(std::function<void()>&& runnable) {
+  static auto method = MessageQueueThread::javaClassStatic()->
+    getMethod<void(Runnable::javaobject)>("runOnQueue");
+  method(m_jobj, JNativeRunnable::newObjectCxxArgs(runnable).get());
+}
+
+/* static */
+std::unique_ptr<JMessageQueueThread> JMessageQueueThread::currentMessageQueueThread() {
+  static auto method = MessageQueueThreadRegistry::javaClassStatic()->
+      getStaticMethod<MessageQueueThread::javaobject()>("myMessageQueueThread");
+  return folly::make_unique<JMessageQueueThread>(method(MessageQueueThreadRegistry::javaClassStatic()));
+}
+
+} }
+

ReactAndroid/src/main/jni/react/jni/JMessageQueueThread.h

@@ -0,0 +1,41 @@
+// Copyright 2004-present Facebook. All Rights Reserved.
+
+#pragma once
+
+#include <functional>
+
+#include <jni/fbjni.h>
+
+using namespace facebook::jni;
+
+namespace facebook {
+namespace react {
+
+class MessageQueueThread : public jni::JavaClass<MessageQueueThread> {
+public:
+  static constexpr auto kJavaDescriptor = "Lcom/facebook/react/bridge/queue/MessageQueueThread;";
+};
+
+class JMessageQueueThread {
+public:
+  JMessageQueueThread(alias_ref<MessageQueueThread::javaobject> jobj);
+
+  /**
+   * Enqueues the given function to run on this MessageQueueThread.
+   */
+  void runOnQueue(std::function<void()>&& runnable);
+
+  /**
+   * Returns the current MessageQueueThread that owns this thread.
+   */
+  static std::unique_ptr<JMessageQueueThread> currentMessageQueueThread();
+private:
+  global_ref<MessageQueueThread::javaobject> m_jobj;
+};
+
+class MessageQueueThreadRegistry : public jni::JavaClass<MessageQueueThreadRegistry> {
+public:
+  static constexpr auto kJavaDescriptor = "Lcom/facebook/react/bridge/queue/MessageQueueThreadRegistry;";
+};
+
+} }