Add workaround for redefinition of __proto__ property.

Add workaround for redefinition of __proto__ property.

This is a temporary workaround when the __proto__ property is being
redefined (e.g. by Object.freeze()) to not loose the foreign callback.
Once the __proto__ property is a real JavaScript accessor this hack is
no longer necessary. This change also makes __proto__ configurable.

R=rossberg@chromium.org
BUG=v8:2565
TEST=mjsunit/regress/regress-2565

Committed: http://code.google.com/p/v8/source/detail?r=13817

[rossberg, 2013-03-04 16:04:42]

https://codereview.chromium.org/12398010/diff/1/src/runtime.cc
File src/runtime.cc (right):

https://codereview.chromium.org/12398010/diff/1/src/runtime.cc#newcode4099
src/runtime.cc:4099: attr = static_cast<PropertyAttributes>(attr & ~READ_ONLY);
As discussed offline, this should also filter DONT_DELETE. More importantly,
DONT_DELETE should be false initially.

[Michael Starzinger, 2013-03-04 16:24:58]

Comments addressed. PTAL.

https://codereview.chromium.org/12398010/diff/1/src/runtime.cc
File src/runtime.cc (right):

https://codereview.chromium.org/12398010/diff/1/src/runtime.cc#newcode4099
src/runtime.cc:4099: attr = static_cast<PropertyAttributes>(attr & ~READ_ONLY);
On 2013/03/04 16:04:42, rossberg wrote:
> As discussed offline, this should also filter DONT_DELETE. More importantly,
> DONT_DELETE should be false initially.

Done.

[rossberg, 2013-03-04 17:31:14]

lgtm

[Michael Starzinger, 2013-03-04 17:53:47]

Committed patchset #2 manually as r13817 (presubmit successful).