Retrieve screen info once

The method getScreenInfo() is synchronized, and the result may change
between calls.

Call it once and store the result in a local variable.

server/src/main/java/com/genymobile/scrcpy/ScreenEncoder.java

@@ -63,8 +63,9 @@ public void streamScreen(Device device, FileDescriptor fd) throws IOException {
             do {
                 MediaCodec codec = createCodec();
                 IBinder display = createDisplay();
-                Rect contentRect = device.getScreenInfo().getContentRect();
-                Rect videoRect = device.getScreenInfo().getVideoSize().toRect();
+                ScreenInfo screenInfo = device.getScreenInfo();
+                Rect contentRect = screenInfo.getContentRect();
+                Rect videoRect = screenInfo.getVideoSize().toRect();
                 setSize(format, videoRect.width(), videoRect.height());
                 configure(codec, format);
                 Surface surface = codec.createInputSurface();