port 5d68529b (r26546)

original commit message:

   Parsing: Make Scope not know about Isolate.

  Scope, like Parser, must be able to operate independent of Isolate and the V8
  heap (for background parsing). After the heap-independent phase, there is a heap
  dependent phase, during which we do operations such as scope anaylysis.

  This CL makes the phases explicit by not telling Scope about the Isolate too
  early (during the heap-independent phase, Scope should know nothing about
  Isolate). This decreases the probability of accidental code changes which would
  add heap-dependent operations into the heap-independent phase.

BUG=
R=weiliang.lin@intel.com

Review URL: https://codereview.chromium.org/913163003

Cr-Commit-Position: refs/heads/master@{#26590}