Make renderState better aware of passState during partialApply.

[emackey]

This changes RenderState.partialApply to be more careful of specific changes to the passState that affect the current renderState. It attempts to keep all of the optimizations from the previous implementation except where they were so aggressive as to miss needed state changes.

With this change, the functions that apply the state transition between two renderStates are not allowed access to the passState at all. The passState is reconciled separately, and is always considered even if the renderStates were identical.

Looks like test coverage is missing from this area of the code, @pjcozzi said it might be hard to test. Perhaps a mock gl context could be constructed with spy listeners, but that likely won't happen for 1.11.

Fixes #2790
Fixes #2811

[emackey]

I also created a branch renderstate-debug with some hacked-in stats to report on how often the various branches in partialApply are applied or skipped. Type stat() at the console to see this.

[pjcozzi]

Thanks @emackey, this looks good.

[pjcozzi]

@emackey

• Can you update CHANGES.md in master?
• Can we delete this branch: https://github.com/AnalyticalGraphicsInc/cesium/compare/renderstate-debug

[mramato]

FYI, I think @emackey it traveling until July 6th, not sure if he'll be checking email. If you want something in CHANGES for 1.11, you'll probably want to just update it yourself.

[emackey]

I moved renderstate-debug over to the emackey fork, to get it out of the main repo. Feel free to make any comments needed in CHANGES.md.