Various cleanup/simplification in object-observe.js
The biggest change is the removal of the map wrapper objects:
we now operate directly on the observation weak map, since there
are already Get/GetOrCreate/Set functions for each info map.
Various other small cleanups as well, including the deletion of
unnecessary forwarding functions and making use of standard macros.
This is a reland of r24972, retaining GetObservationStateJS() to
keep snapshotting working properly.
R=rossberg@chromium.org
Review URL: https://codereview.chromium.org/
663253006
Cr-Commit-Position: refs/heads/master@{#24990}
git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24990
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