Previously GetSharedFunctionInfoForStreamedScript didn't either check the
compilation cache or put the result of compilation into the compilation
cache. This would mean future compiles would need to re-parse / compile
the same script even if the isolate had already seen it. This CL
fixes this.

Also refactors the compilation pipelines to ensure we call debug->OnAfterCompile()
for all script compiles even when loading from a cache.

BUG=v8:5203

Change-Id: I4b06bdfc566425f4e6d70fc3e6e080b0dc497d48
Reviewed-on: https://chromium-review.googlesource.com/939464
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Mythri Alle <mythria@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51607}