Small improvements into Graph example

Use FrameAnimation instead of Timer and double the amount of samples
to make the example smoother.

Change-Id: I6f5bb1414fd7532e16aeb25f886879828ce29854
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>
Reviewed-by: Tomi Korpipää <tomi.korpipaa@qt.io>
(cherry picked from commit 75a33aceab)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

examples/quick/scenegraph/graph/main.qml

@@ -15,27 +15,23 @@ Item {
         anchors.margins: 100
 
         function newSample(i) {
-            return (Math.sin(i / 100.0 * Math.PI * 2) + 1) * 0.4 + Math.random() * 0.05;
+            return (Math.sin(i / 200.0 * Math.PI * 2) + 1) * 0.4 + Math.random() * 0.05;
         }
 
         Component.onCompleted: {
-            for (var i=0; i<100; ++i)
+            for (var i=0; i<graph.offset; ++i)
                 appendSample(newSample(i));
         }
 
-        property int offset: 100;
+        property int offset: 200
     }
 
-    Timer {
-        id: timer
-        interval: 500
-        repeat: true
+    FrameAnimation {
         running: true
         onTriggered: {
             graph.removeFirstSample();
             graph.appendSample(graph.newSample(++graph.offset));
         }
-
     }
 
     Rectangle {