android: Java-based launcher thread

base/test/android/java_handler_thread_for_testing.cc

Index: base/test/android/java_handler_thread_for_testing.cc
diff --git a/base/test/android/java_handler_thread_for_testing.cc b/base/test/android/java_handler_thread_for_testing.cc
index fe5234761cbbc3e0095ce81b4ce3641ccecfc107..c5cd1c35ff4f9bce2aab6c236075ee27a01bd24b 100644
--- a/base/test/android/java_handler_thread_for_testing.cc
+++ b/base/test/android/java_handler_thread_for_testing.cc
@@ -5,6 +5,7 @@
 #include "base/test/android/java_handler_thread_for_testing.h"
 
 #include "base/message_loop/message_loop.h"
+#include "jni/JavaHandlerThreadTest_jni.h"
 
 namespace base {
 namespace android {
@@ -26,13 +27,18 @@ JavaHandlerThreadForTesting::JavaHandlerThreadForTesting(
       message_handler_factory_(new TestJavaMessageHandlerFactory()),
       test_done_event_(test_done_event) {}
 
+JavaHandlerThreadForTesting::JavaHandlerThreadForTesting(
+    base::WaitableEvent* test_done_event)
+    : JavaHandlerThread(Java_JavaHandlerThreadTest_testAndGetJavaHandlerThread(
+          base::android::AttachCurrentThread())),
+      message_handler_factory_(new TestJavaMessageHandlerFactory()),
+      test_done_event_(test_done_event) {}
+
 JavaHandlerThreadForTesting::~JavaHandlerThreadForTesting() = default;
 
 void JavaHandlerThreadForTesting::StartMessageLoop() {
   static_cast<MessageLoopForUI*>(message_loop_.get())
-      ->StartForTesting(
-          message_handler_factory_.get(),
-          reinterpret_cast<base::WaitableEvent*>(test_done_event_));
+      ->StartForTesting(message_handler_factory_.get(), test_done_event_);
 }
 
 void JavaHandlerThreadForTesting::StopMessageLoop() {