runOnAndroidMainThread(): optimize shared pointer use

- port from QSharedPointer to std::shared_ptr (one instead of two
  atomic ops per shared-pointer copy)

- port to std::make_shared (one instead of two memory allocations for
  shared-pointer + payload creation)

Pick-to: 6.5
Change-Id: Idecef5732d181a63e6936f54204eeb7ecbdc4a0f
Reviewed-by: Assam Boudjelthia <assam.boudjelthia@qt.io>

src/corelib/platform/android/qandroidnativeinterface.cpp

@@ -12,6 +12,7 @@
 #include <QtCore/qpromise.h>
 #include <QtCore/qthreadpool.h>
 #include <deque>
+#include <memory>
 #endif
 
 QT_BEGIN_NAMESPACE
@@ -21,7 +22,7 @@ static const char qtNativeClassName[] = "org/qtproject/qt/android/QtNative";
 
 struct PendingRunnable {
     std::function<QVariant()> function;
-    QSharedPointer<QPromise<QVariant>> promise;
+    std::shared_ptr<QPromise<QVariant>> promise;
 };
 
 using PendingRunnables = std::deque<PendingRunnable>;
@@ -161,7 +162,7 @@ QFuture<QVariant> QNativeInterface::QAndroidApplication::runOnAndroidMainThread(
                                                     const std::function<QVariant()> &runnable,
                                                     const QDeadlineTimer timeout)
 {
-    QSharedPointer<QPromise<QVariant>> promise(new QPromise<QVariant>());
+    auto promise = std::make_shared<QPromise<QVariant>>();
     QFuture<QVariant> future = promise->future();
     promise->start();