Use original shader if fail at assembling new shader module (#1254)
Use original shader if fail at assembling new shader module (#1254)

* Use original shader if fail at assembling new shader module

Also drop stale comments.

Fix #1247
google/gapid,baldwinn860/gapid,google/agi,baldwinn860/gapid,google/agi,baldwinn860/gapid,pmuetschard/gapid,baldwinn860/gapid,Qining/gapid,google/agi,baldwinn860/gapid,Qining/gapid,baldwinn860/gapid,google/agi,dsrbecky/gapid,pmuetschard/gapid,dsrbecky/gapid,dsrbecky/gapid,google/gapid,dsrbecky/gapid,google/gapid,pmuetschard/gapid,Qining/gapid,google/agi,google/agi,pmuetschard/gapid,Qining/gapid,google/gapid,google/gapid,Qining/gapid,google/gapid,pmuetschard/gapid,Qining/gapid,pmuetschard/gapid,baldwinn860/gapid,dsrbecky/gapid,google/agi,pmuetschard/gapid,Qining/gapid,baldwinn860/gapid,google/agi,google/gapid,dsrbecky/gapid,dsrbecky/gapid,Qining/gapid,google/gapid,pmuetschard/gapid,dsrbecky/gapid