Android: correctly use mutex for texture rendering.

Some sections were not protected by the mutex, even though they should
have been. An example of problem that could happen because of this was
if the SurfaceTexture was reset while the render thread was rendering
that texture.

Change-Id: Ie95860fd4eb722bbac04cccc430cc1a8abf1df4d
Reviewed-by: Christian Stromme <christian.stromme@theqtcompany.com>

src/plugins/android/src/common/qandroidvideooutput.cpp

@@ -218,6 +218,8 @@ bool QAndroidTextureVideoOutput::initSurfaceTexture()
         return false;
     }
 
+    QMutexLocker locker(&m_mutex);
+
     m_surfaceTexture = new AndroidSurfaceTexture(m_externalTex);
 
     if (m_surfaceTexture->surfaceTexture() != 0) {
@@ -235,6 +237,7 @@ bool QAndroidTextureVideoOutput::initSurfaceTexture()
 
 void QAndroidTextureVideoOutput::clearSurfaceTexture()
 {
+    QMutexLocker locker(&m_mutex);
     if (m_surfaceTexture) {
         delete m_surfaceTexture;
         m_surfaceTexture = 0;