Auto merge of #3255 - nical:scene-indicator, r=gw3583
Auto merge of #3255 - nical:scene-indicator, r=gw3583

Properly track whether a new scene has been built to fix the debug indicator

I broke the new scene indicator when when removing redundant frame builds. Now that we don't necessarily send a new frame to the renderer when the scene is built, the information is lost so we have store it somewhere.

r? anyone

Fixes #3247.

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