`WebGLRenderer#clear` does not always clear main framebuffer

Description of the problem

WebGLRenderer#clear does not always clear main framebuffer. When clearTarget it calls setRenderTarget and doesn’t revert back to the previous (i.e. default) one. If clear is called next, it will clear again WebGLRenderTarget provided to clearTarget, not main framebuffer as expected.

Expected behavior: clear always clears main framebuffer (canvas), while clearTarget clears provided render target.

Revelant code:

• https://github.com/mrdoob/three.js/blob/master/src/renderers/WebGLRenderer.js#L506
• https://github.com/mrdoob/three.js/blob/master/src/renderers/WebGLRenderer.js#L536

Three.js version

• Dev
• r79
• …

Browser

• All of them
• Chrome
• Firefox
• Internet Explorer

OS

• All of them
• Windows
• Linux
• Android
• IOS

Hardware Requirements (graphics card, VR Device, …)

Irrevelant