Add a --harmony-object-observe runtime flag (on by default)

Add a --harmony-object-observe runtime flag (on by default)

To avoid tanking context startup performance, only the actual installation of the
JS-exposed API is flag-guarded. The remainder of the implementation still
resides in the snapshot.

Committed: https://crrev.com/2e4efcfac243268177dc34f4805cd2739d84dbd5
Cr-Commit-Position: refs/heads/master@{#30017}

[adamk, 2015-08-04 00:11:17]

adamk@chromium.org changed reviewers:
+ rossberg@chromium.org

[rossberg, 2015-08-04 12:44:22]

lgtm

[adamk, 2015-08-04 18:07:57]

The CQ bit was checked by adamk@chromium.org

[adamk, 2015-08-04 18:07:57]

The patchset sent to the CQ was uploaded after l-g-t-m from
rossberg@chromium.org
Link to the patchset: https://codereview.chromium.org/1257063003/#ps20001
(title: "Merged")

[commit-bot: I haz the power, 2015-08-04 18:08:07]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1257063003/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1257063003/20001

[commit-bot: I haz the power, 2015-08-04 18:16:47]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-08-04 18:16:48]

Try jobs failed on following builders:
  v8_linux64_avx2_rel on tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux64_avx2_rel/builds/...)

[adamk, 2015-08-04 20:15:34]

Had to add some code to remove function prototypes during snapshot generation
(assume this has something to do with serialization). WIthout that,
%FunctionSetPrototype would fail the assertion in JSFunction::RemovePrototype
that the functions had the proper map.

Added a TODO to investigate more, but this seems to work for now (the second
call to %FunctionSetPrototype will bail out immediately).

[adamk, 2015-08-04 20:16:02]

The CQ bit was checked by adamk@chromium.org

[adamk, 2015-08-04 20:16:02]

The patchset sent to the CQ was uploaded after l-g-t-m from
rossberg@chromium.org
Link to the patchset: https://codereview.chromium.org/1257063003/#ps40001
(title: "Move some initialization back to the snapshot")

[commit-bot: I haz the power, 2015-08-04 20:16:18]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1257063003/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1257063003/40001

[commit-bot: I haz the power, 2015-08-04 20:53:30]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-08-04 20:53:40]

Patchset 3 (id:??) landed as
https://crrev.com/2e4efcfac243268177dc34f4805cd2739d84dbd5
Cr-Commit-Position: refs/heads/master@{#30017}