Previously, if an unbound script was created in a non-inspected context,
but later bound to an inspected one, it never appeared in the
debugger sources.

After this change `OnAfterCompile` will be invoked not on the original
script compilation, but when it's actually bound to a context for
execution, which means `Debugger.scriptParsed` will be now sent to the
inspector even for such precompiled scripts.

R=jgruber@chromium.org, kozyatinskiy@chromium.org, yangguo@chromium.org

Bug: v8:7654
Change-Id: Ice13312e425903fb2baf14edab5c566d649a6438
Reviewed-on: https://chromium-review.googlesource.com/1013581Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52652}