Camera setView / flyTo rectangle produces inconsistent results in 2D with a narrow / portrait map viewer

[pjaustin]

When in 2D mode, calling camera.setView({ destination: rectangle }); or camera.flyTo({ destination: rectangle }); displays a larger area than expected when the map viewer is narrow / portrait.

Typically, the above functions result in a view where the rectangle fills the screen (i.e. the camera is centred of over the rectangle and zoomed in as far as possible such the view still contains the whole rectangle). This behaviour appears to work consistently in 3D and CV, and most of the time in 2D, except when the map viewer is narrow / portrait, in which case the camera is not zoomed in as far as it could be, and a larger area than necessary is displayed.

Steps to reproduce:

• Open sandcastle camera examples: https://cesiumjs.org/Cesium/Build/Apps/Sandcastle/index.html?src=Camera.html
• Resize either the map viewer pane or the browser as a whole such that the map viewer is narrow / portrait (the issue is sometimes more apparent with rectangles that are tall and narrow, but the default rectangles in the examples are sufficient to reproduce this).
• Set the globe to 2D.
• From the drop down menu in the example, select "Fly to Rectangle" / "View a Rectangle".

[hpinkos]

Related #2473

[hpinkos]

@angrycat9000 ran into this issue today. flyTo/setView doesn't zoom as close to the rectangle as it can when the canvas aspect ratio is portrait instead of landscape.

sandcastle