Add regression test for issue CesiumGS#6812

Specs/Scene/SceneSpec.js

@@ -1357,6 +1357,32 @@ defineSuite([
         scene.destroyForSpecs();
     });
 
+    it('changing the camera frustum does not cause continuous rendering in requestRenderMode', function() {
+        var scene = createScene();
+
+        scene.renderForSpecs();
+
+        var lastRenderTime = JulianDate.clone(scene.lastRenderTime, scratchTime);
+        expect(lastRenderTime).toBeDefined();
+        expect(scene._renderRequested).toBe(false);
+
+        scene.requestRenderMode = true;
+        scene.maximumRenderTimeChange = undefined;
+
+        scene.camera.frustum.near *= 1.1;
+
+        // Render once properly
+        scene.renderForSpecs();
+        expect(scene.lastRenderTime).not.toEqual(lastRenderTime);
+
+        // Render again - but this time nothing should happen.
+        lastRenderTime = JulianDate.clone(scene.lastRenderTime, scratchTime);
+        scene.renderForSpecs();
+        expect(scene.lastRenderTime).toEqual(lastRenderTime);
+
+        scene.destroyForSpecs();
+    });
+
     it('successful completed requests causes a new frame to be rendered in requestRenderMode', function() {
         var scene = createScene();