Android: fixes some issues with JCamera.

- Quit the worker thread only when the worker is deleted. This makes
sure all events are processed before terminating the worker.
- Correctly cache the preview size even when it's an invalid one.

Task-number: QTBUG-36204
Change-Id: I76055984e8ece3f7f40dba7dd89d28a4faa1e72e
Reviewed-by: Denis Kormalev <dkormalev@ics.com>
Reviewed-by: Christian Stromme <christian.stromme@digia.com>

src/plugins/android/src/wrappers/jcamera.cpp

@@ -151,6 +151,7 @@ class JCameraWorker : public QObject, public QJNIObjectPrivate
     friend class JCamera;
 
     JCameraWorker(JCamera *camera, int cameraId, jobject cam, QThread *workerThread);
+    ~JCameraWorker();
 
     Q_INVOKABLE void release();
 
@@ -275,9 +276,7 @@ JCamera::~JCamera()
         g_objectMap.remove(d->m_cameraId);
         g_objectMapMutex.unlock();
     }
-    QThread *workerThread = d->m_workerThread;
     d->deleteLater();
-    workerThread->quit();
 }
 
 JCamera *JCamera::open(int cameraId)
@@ -372,7 +371,7 @@ void JCamera::setPreviewSize(const QSize &size)
     d->m_parametersMutex.lock();
     bool areParametersValid = d->m_parameters.isValid();
     d->m_parametersMutex.unlock();
-    if (!areParametersValid || !size.isValid())
+    if (!areParametersValid)
         return;
 
     d->m_previewSize = size;
@@ -661,6 +660,11 @@ JCameraWorker::JCameraWorker(JCamera *camera, int cameraId, jobject cam, QThread
     }
 }
 
+JCameraWorker::~JCameraWorker()
+{
+    m_workerThread->quit();
+}
+
 void JCameraWorker::release()
 {
     m_previewSize = QSize();