Simplify, speed-up correct-context ObjectObserve calls

Simplify, speed-up correct-context ObjectObserve calls

The original patch which ensured that Object.observe did allocations in the correct context regressed performance about 12%. This patch gets back most of that (about 11%) by simply returning the correct function which is then directly callable from JS, rather than by making the call from the runtime function. A side-effect is that their implementation is shorter.

LOG=Y
BUG=NONE
R=verwaest@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=21575

[rafaelw, 2014-05-27 23:48:42]

https://codereview.chromium.org/307543008/diff/50001/src/objects.h
File src/objects.h (right):

https://codereview.chromium.org/307543008/diff/50001/src/objects.h#newcode8797
src/objects.h:8797: kArrayIndexValueBits> {}
These aren't a part of this change. git-cl was complaining about style, so I
went ahead and cleaned this up.

[Toon Verwaest, 2014-05-28 10:54:41]

lgtm

[rafaelw, 2014-05-28 19:13:48]

Committed patchset #5 manually as r21575 (presubmit successful).