Create magnifier bench scene

Test: this
Change-Id: Iea1033fda55ff0946b5cd8d28ecba29453b937ca
diff --git a/libs/hwui/tests/macrobench/TestSceneRunner.cpp b/libs/hwui/tests/macrobench/TestSceneRunner.cpp
index 3eb58a9..9428f53 100644
--- a/libs/hwui/tests/macrobench/TestSceneRunner.cpp
+++ b/libs/hwui/tests/macrobench/TestSceneRunner.cpp
@@ -111,8 +111,6 @@
     // Switch to the real display
     gDisplay = getBuiltInDisplay();
 
-    std::unique_ptr<TestScene> scene(info.createScene(opts));
-
     Properties::forceDrawFrame = true;
     TestContext testContext;
     testContext.setRenderOffscreen(opts.renderOffscreen);
@@ -122,6 +120,9 @@
     const int height = gDisplay.h;
     sp<Surface> surface = testContext.surface();
 
+    std::unique_ptr<TestScene> scene(info.createScene(opts));
+    scene->renderTarget = surface;
+
     sp<RenderNode> rootNode = TestUtils::createNode(
             0, 0, width, height, [&scene, width, height](RenderProperties& props, Canvas& canvas) {
                 props.setClipToBounds(false);