Liveedit step-by-step:
1. calculate diff between old source and new source,
2. map function literals from old source to new source,
3. create new script for new_source,
4. mark literals with changed code as changed, all others as unchanged,
5. check that for changed literals there are no:
  - running generators in the heap,
  - non droppable frames (e.g. running generator) above them on stack.
6. mark the bottom most frame with changed function as scheduled for
   restart if any.
7. for unchanged functions:
  - deoptimize,
  - remove from cache,
  - update source positions,
  - move to new script,
  - reset feedback information and preparsed scope information if any,
  - replace any sfi in constant pool with changed one if any.
8. for changed functions:
  - deoptimize
  - remove from cache,
  - reset feedback information,
  - update all links from js functions to old shared with new one.
9. swap scripts.

TBR=ulan@chromium.org

Bug: v8:7862,v8:5713
Cq-Include-Trybots: luci.chromium.try:linux_chromium_headless_rel;luci.chromium.try:linux_chromium_rel_ng;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I8f6f6156318cc82d6f36d7ebc1c9f7d5f3aa1461
Reviewed-on: https://chromium-review.googlesource.com/1105493Reviewed-by: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54146}