Set proper symbol ids on temporary symbol nodes Temporary symbols used to all have symbol id 0. Now they get assigned unique symbol ids. This makes it possible to keep track of them according to the symbol id instead of their name, paving way to more robust AST handling in the future. BUG=angleproject:1490 TEST=angle_unittests Change-Id: I292e2e483cc39173524fd30a30b48c4c808442e5 Reviewed-on: https://chromium-review.googlesource.com/559335 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Corentin Wallez <cwallez@chromium.org> Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>