Instead of creating a runtime call for the static class field
initializer in the AST, we do it in the bytecode generator.

This adds the initializer function to the ClassLiteral AST node.

Bug: v8:5367
Change-Id: Iffaa6531511023812011ee19fc96cea9e5c9d3f3
Reviewed-on: https://chromium-review.googlesource.com/736315Reviewed-by: Georg Neis <neis@chromium.org>
Reviewed-by: Mythri Alle <mythria@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Sathya Gunasekaran <gsathya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49008}