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This adorns ScriptStates with a unique identifier, and adds
lifecycle tracking instrumentation hooks. A further CL will
wire this up in order to implement detached context tracking
as part of the performance.measureMemory API.

BUG=1085129

Change-Id: I4ddb84c547430a28615dea57e7fd346c9e27b1f5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2327851
Commit-Queue: Chris Hamilton <chrisha@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Will Harris <wfh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#795477}