getUserDefinedVariableInfo.

BUG=angle:654

Change-Id: I07a230bbf2387e85168c50cb3719c669a7890f8a
Reviewed-on: https://chromium-review.googlesource.com/199687Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
Tested-by: Shannon Woods <shannonwoods@chromium.org>