SkSL: Variable references are never "isConstant"

isConstant really means "has a known value at compile time", but for
variables declared with "const", the two meanings had been conflated.
There were several ways for this to produce surprising error messages.
The included unit test crashed before removing the override, and now

Change-Id: I49b926e51c421db93240cbbf42231de0444358d6
Reviewed-by: John Stiles <>
Commit-Queue: Brian Osman <>
2 files changed